Britain’s Thermonuclear Bluff

Norman Dombey and Eric Grove

‘Britain Carries Out Second H-Test, Explosion even bigger than the first one,’ the Manchester Guardian reported on Saturday, 1 June 1957. It was the lead news item. The story that followed was datelined ‘Aboard HMS Alert’, Alert being the frigate which housed the representatives of the British press corps invited to see for themselves that Britain, as befitted the third great power in the world, had attained thermonuclear status. According to Reuters, ‘a great multi-coloured fireball above the central Pacific heralded Britain’s second hydrogen bomb test’ off the Malden Islands.

In retrospect, there are two problems with these accounts. First, the test of Orange Herald was held on Friday, 31 May: it would not have been physically possible for the story to appear before the following Monday. In other words, the journalists wrote their stories in advance of the test, on the basis of a briefing from Brigadier Jehu, who had seen the first test – Short Granite – of the 1957 Grapple series on 15 May. Secondly, it now appears very probable that Orange Herald was not an H-bomb at all, but a large A-bomb. Journalists, after all, could not be expected to differentiate between mushroom clouds, and no figures were issued then (or have been since) about the size of the test.

To this day the British Government is very reluctant to give any details about the thermonuclear programme it embarked on 38 years ago: certainly we know more about the early stages of the Soviet thermonuclear programme than we do about the British. However, three things have made it possible for us to attempt a reconstruction of events between 1954 and 1958: an unusually forthcoming obituary, in the Biographical Memoirs of the Fellows of the Royal Society, of Sir William Cook, scientific director of the Grapple test series; some recent disclosures on the part of John Ward, who was employed at the British nuclear weapons laboratory at Aldermaston for six months during 1955; and a group of declassified US documents obtained by Robert Norris of the Natural Resources Defence Council in Washington. It may well be that there are errors in our account – given the habits of secrecy and misinformation which prevail among British governments it could perhaps hardly be otherwise – but what follows is at least an introduction to the issues.

The Orange Herald test was only the most blatant example of Britain’s thermonuclear bluff: it seems that none of the four nuclear tests held in 1957 was a hydrogen bomb test as we now understand it. But the tests had as much to do with public relations, and especially relations with the United States, as with constructing an authentic hydrogen bomb, and the bluff was remarkably successful. Within four years of Churchill’s decision to launch a British H-bomb programme, Britain’s overriding political objective – a special nuclear relationship with the United States – had been achieved. That this goal was reached appears to have been due mainly to the contribution of the physicist John Ward. The closeness of the US-UK special relationship in nuclear weapons which resulted from the combination of this bluff and Ward’s genius has also been a carefully kept secret. In fact, from 1958 onwards the United States transferred to Britain detailed design drawings and material specifications of many of their most modern hydrogen bombs so that Britain could manufacture these US weapons as its own. The story we tell has its ironies: Britain’s initial reason for developing its own H-bombs was that it wanted to be in a position to influence US nuclear policy, but the US ended up with substantial power over British nuclear policy.

There are two basic methods of obtaining usable nuclear energy: fission, or the splitting up of heavy elements into lighter elements, and fusion, where light elements combine to make heavier elements. This defines the distinction between A-bombs and H-bombs: A-bombs are fission bombs where the fuel is uranium-235 or plutonium-239. H-bombs are fusion bombs where the hydrogen isotopes deuterium (hydrogen-2) and tritium (hydrogen-3) form the fuel. The reason these weapons are also called thermonuclear is that temperatures comparable to the temperature of the Sun are needed to initiate the nuclear fusion process. Both the fission and fusion processes liberate substantial amounts of energy, but while the yield of an A-bomb is characteristically measured in kilotons, that of an H-bomb can reach many megatons or millions of tons of high explosive.

Tritium is often added to fission weapons to provide some fast neutrons from thermonuclear processes in order to increase the yield of the weapon. The weapon is still referred to as a fission weapon, however, because almost all the explosive energy comes from fission, not fusion. It is worth bearing in mind that it was exceedingly difficult for the United States to develop megaton hydrogen bombs in which a significant part of the energy came from fusion. Although President Truman had authorised the H-bomb programme in 1950, calculations later that year on one of the world’s first electronic computers showed that the hydrogen bomb design on which the weapons laboratory at Los Alamos had been working since the mid-Forties was fundamentally flawed. The ‘Super’, as the early hydrogen bomb was known, would have blown itself apart before any appreciable thermonuclear processes were initiated.

Edward Teller and Stanislaw Ulam, émigré scientists from Hungary and Poland respectively, who were working at Los Alamos, found an ingenious solution in 1951. As part of his work on improved fission weapons Ulam had suggested a two-stage fission design. Teller seized on this idea and proposed a first fission stage which would set off a separate fusion stage by means of X-rays transmitted from the fission explosion. Since X-rays are a form of electromagnetic radiation they travel at the speed of light and thus can in principle implode and ignite the thermonuclear fuel before the shock wave from the primary stage blows it apart. This process is known as radiation implosion; and according to normal US nomenclature, a ‘hydrogen’ or ‘thermonuclear’ bomb refers to a weapon which incorporates the Ulam-Teller concept of two (or more) stages and radiation implosion. A prototype H-bomb, ‘Mike’, incorporating these principles was first successfully tested in November 1952 and was followed by the Castle series at Bikini between March and May 1954 in which several thermonuclear weapons with yields larger than one megaton were tested.

In August 1953 the Soviet Union exploded a large nuclear weapon, known in the West as Joe-4, which it announced was thermonuclear. US weapon scientists have known for some time, however, that the yield of Joe-4 was only about 200-300 kilotons and that it was therefore unlikely to have been a hydrogen bomb in the Ulam-Teller sense. This has recently been confirmed by Soviet physicists writing about Sakharov’s role in the project. Joe-4 was a ‘layer-cake’ device with layers of light and heavy elements. The light elements were in the form of the thermonuclear fuel lithium-6-deuteride and the heavy elements were plutonium, uranium-235 and uranium-238. The latter isotope is then fissioned by fast neutrons from the thermonuclear reaction. By far the greater part of the energy of Joe-4 still came from fission, not fusion, so we will follow US terminology by referring to such weapons as thermonuclear-boosted fission weapons rather than thermonuclear weapons or H-bombs. Such boosted fission weapons are not as efficient as two-stage radiation implosion H-bombs and would not be expected to have yields as large as one megaton.

The British decision to build a hydrogen bomb was taken by a sub-committee of the Churchill Cabinet in 1954, in the aftermath of the US Castle test series. The power of those weapons – one reached 15 megatons – seems to have come as a surprise to everyone including the weapon designers, and the British Government decided that they were too dangerous a capability to be left to the US alone. Churchill felt ‘that we could not expect to maintain our influence as a world power unless we possessed the most up-to-date nuclear weapons,’ while the Chiefs of Staff emphasised the need to have as much influence as possible over the use of the H-bomb. So the aims of British thermonuclear policy were political rather than military right from the start: prestige and a US-UK special nuclear relationship were the objectives.

The Churchill Government’s decision put Sir William (later Lord) Penney, the Director of Aldermaston, in a difficult position. He did not know the details of Ulam and Teller’s discovery yet he had been instructed to produce a thermonuclear weapon in the megaton range for use as a warhead with the Blue Steel air-launched missile and Blue Streak long-range ballistic missile. A limited number (twenty or so, according to Admiralty papers) of free-fall bombs for the V-bombers were also required. In 1955 the situation became even trickier for Penney as public outcry over radioactive fallout from nuclear weapons tests led to preliminary discussions between the US and the USSR about a nuclear test-ban treaty. A test-ban treaty or even a voluntary moratorium on testing would have prevented any demonstration by Britain of its own thermonuclear capability, real or otherwise.

By 1954 British nuclear weapon designers had produced a fission weapon for the RAF’s future strategic bombers. The first British experimental fission device, with a yield of 25 kilotons, had been successfully tested in the Monte Bello islands off Australia in October 1952. Getting this far had not been particularly difficult. Penney and several members of his team had been members of the Manhattan Project in the US during the war and knew what to do. The main problem was to accumulate enough plutonium, and reactors at Windscale were built for this purpose. After some further tests in Australia, the first Blue Danube bomb was delivered to the RAF in November 1953.

Blue Danube had a yield of 20-40 kilotons and was comparable to the early American B-4 weapon which went into service in 1949. It was long and streamlined unlike the short fat B-4 but its weight of around ten thousand pounds and its size meant that it was unsuitable for the RAF’s only available jet bomber, the Canberra. Blue Danube did not go into operation with the RAF’s first V-bomber squadrons until 1956. Meanwhile work at Aldermaston was concentrated on a smaller fission bomb that could achieve a yield comparable to Blue Danube but at only 20 per cent of the weight. This weapon, code-named Red Beard, would be carried by RAF Canberras and Naval fighter-bombers.

William Cook was put in charge of the thermonuclear programme at Aldermaston in September 1954. Until then the British had been able to capitalise on their participation in the Manhattan Project: now they were almost entirely on their own. The US Atomic Energy (McMahon) Act of 1946 forbade the Government to share its nuclear weapon information with any other country including Britain. There were just two exceptions: intelligence about the 1953 Soviet nuclear tests was shared between the US and UK and Britain had been allowed to collect air samples during the 1954 Castle series. With discussions between the US and the USSR on a nuclear-test-ban treaty under way, time was short. It was essential for Penney and Cook to begin immediately planning for tests in Australia or the Pacific. The information from Joe-4 showed that lithium-6-deuteride and uranium 238 had played an essential role in the weapon. So a line of development involving lithium-6-deuteride and uranium 238 had to be pursued urgently. Indeed, two different thermonuclear-boosted designs were pursued: we know this because a declassified report of a US-UK meeting of weapon scientists in September 1958 refers to the UK demonstrating ‘two boosted fission designs’.

A primitive layer-cake design involving lithium deuteride and uranium-238 was tested on a tower in the G2 test of the Mosaic series in Australia in 1956. It was very successful: the British Government pretended for nearly thirty years that the yield was 60 kilotons, but after repeated questioning by Justice McLellan’s Royal Commission on the Australian tests, documents were released in 1985 showing that the yield was 98 kilotons. In her account of the G2 test, in A Very Special Relationship, Lorna Arnold confirms the use in the test of lithium hydride to initiate thermonuclear processes and thus fission uranium 238. Lithium hydride is presumably a euphemism for lithium deuteride.

The yield of each of the three 1957 tests in the Pacific was not specified but was stated to be ‘in the megaton range’. The phrase originates in the statement Anthony Eden made to the House of Commons in June 1956 announcing that the Grapple series would be held the following year and that they would be thermonuclear tests ‘in the megaton range’. Furthermore Eden assured the House that ‘the tests will be high air bursts which will not involve heavy fall-out.’ The tests were duly held and government spokesmen duly announced that each was ‘in the megaton range’ and that ‘the local fall-out was almost negligible,’ to quote Mr Macmillan after Short Granite. Much has been written about the far-from-negligible effects of the fall-out from these tests on the servicemen involved, but up to now there has been no serious questioning of the phrase ‘in the megaton range’. What is clear is that the British Government has something to hide: 35 years after the Grapple series it has not given any yield figures for the three tests. But it has revealed under pressure from the Australian Royal Commission that ‘in the megaton range’ does not mean ‘about one megaton’ or ‘over one megaton’ but ‘a few hundred kiloton to several megaton’. In our view, which is shared by Robert Norris in the forthcoming edition of the Nuclear Weapons Databook, the 1957 Grapple series in fact consisted of tests of the two versions of thermonuclear-boosted fission weapons revealed in the report of the US-UK meeting of September 1958, together with a high-yield A-bomb also cited in the US document and revealed in the Cook obituary, where it was referred to as a ‘fallback’. None of these designs would produce anything like a megaton. Dr Herbert York, then Director of the Livermore nuclear weapons laboratory, was a US observer of Short Granite, the first Grapple test. He told us that he made a rough estimate of its yield from the angular size of the fireball and concluded that it was less than half a megaton.

The fallback was to be an extension of the lightweight plutonium fission bomb Red Beard, then under development, which would be ‘expensive in fissile material’ according to Cook’s biographers, one of whom was Penney. It was thus similar in concept to the high-yield A-bomb tested by the US in 1952 where a yield of 500 kilotons was achieved. It is unlikely that Britain had as much fissile material to waste as the US, so 300 kilotons would be a conservative estimate of its yield. Cook’s obituary reveals that one of the three Grapple tests was a test of the ‘fallback’, which, as we’ve said, was most likely to have been Orange Herald. For one thing, ‘Granite’ seems to have been used to designate a thermonuclear capability; the usually well-informed Times Science Correspondent wrote after the Short Granite test that its purpose had been to decide on the appropriate ratios of lithium and hydrogen isotopes, which would confirm that it involved thermonuclear material. In addition, it would be less risky to test a fission A-bomb in front of journalists than an untried design: Penney, according to those who knew him, would have appreciated the joke of testing a fission weapon in front of journalists and saying that it was thermonuclear.

After the Grapple tests of May and June 1957, there was the Grapple X test on 8 November 1957. This test is not referred to in Cook’s obituary as a test of a thermonuclear device; nor is it referred to as thermonuclear in Penney’s obituary in the Times. It seems likely therefore that it was a further test of the ‘fallback’ high-yield fission device. This hypothesis is strengthened by an extremely informative article on ‘The Post-War Bomber Force and the Strategic Deterrent’ in a recent History of the Royal Air Force, which tells us that Bomber Command’s first ‘megaton’ weapon, the Yellow Sun free-fall bomb, was delivered to the RAF on a ‘limited approval’ basis in the summer of 1958 for use by Vulcans operating from British airfields. The US report of the US-UK meeting in September 1958 refers to the British ‘high-yield fission bomb now in stockpile’. It would have been sensible to have a further test of the fission ‘fallback’ in November 1957 prior to it going into service.

John Ward had been recruited to Aldermaston in 1955 so that Britain could build real megaton hydrogen bombs. A brilliant young theoretical physicist, he was already internationally famous for the ‘Ward Identity’, a basic theorem of quantum physics. Sakharov has described him as one of six ‘titans’ of modern physics for their contributions to quantum electrodynamics: three of the ‘titans’, Feynman, Schwinger and Tomonaga, were to receive the Nobel Prize for this work in 1965. Subsequently Ward collaborated with Abdus Salam of Imperial College on a series of papers on the unification of weak and electromagnetic interactions for which Salam (and two other physicists) received the Nobel Prize in 1979. Ward did, however, receive some consolation prizes: the Danny Heineman Prize, the premier US distinction for theoretical physics, was awarded to him in 1980 as was the Hughes Medal of the Royal Society in 1983.

Lord Cherwell, Churchill’s scientific adviser, had heard about Ward from a colleague and insisted over Penney’s head that he be recruited to Aldermaston from the Institute for Advanced Study in Princeton. Ward has described taking up his post there as head of the Green Granite project early in 1955 and ‘to my amazement’ finding that ‘I was assigned the improbable job of uncovering the secret of the Ulam-Teller invention … an idea of genius far beyond the talents of the personnel at Aldermaston, a fact well-known to both Cook and Penney.’ Cook had no pretensions as a physicist. Penney was an expert on instrumentation for measuring blast and radiant heating. He had no special competence in either nuclear physics or the physics of matter at extremely high temperatures (now called plasma physics). Nor were there any theoretical physicists at Aldermaston, apart from Ward, who were anything like as distinguished as those involved either in the US thermonuclear programme where Bethe, Fermi and Teller had all been employed as consultants (von Neumann and Ulam were mathematicians), or in the Soviet thermonuclear programme where Sakharov, Tamm, Zeldovich and Ginzburg were full-time workers at the Installation, the USSR’s secret nuclear-weapons laboratory. Some extremely bright British theoretical physicists (e.g. Bell, Flowers, Skyrme, Marshall) were employed by the Atomic Energy Authority in the mid-Fifties but they were down the road at Harwell and could not be consulted.

Penney was none too happy to have this high-flier imposed on him by Lord Cherwell and never got on well with Ward. The bad feeling was reciprocated. Ward has described going into his office for the first time and finding a detailed design of the ‘Super’ in front of him, presumably courtesy of MI6 and perhaps the CIA too, who knew it did not work. (There is a Churchill minute to his Foreign Secretary dated 1 January 1955 in which he states that ‘we have the secret of the H-bomb’: he may well be referring to the acquisition of the ‘Super’ design.) Penney evidently did not believe that Ward could fulfil the task which he had given him; and when, within six months of taking up his position, Ward had worked out radiation implosion by himself Penney was none too pleased. ‘If this were wartime we might consider something along the lines of these waveguides of yours,’ Ward recalls him saying. Ward was dismayed at the lack of support that he was getting and went back to the US. Cook was more sympathetic and arranged for Keith Roberts, who knew the details of the Ward proposal, and Bryan Taylor, who had just joined the Aldermaston staff, to continue work on two-stage radiation implosion devices. They were assisted in the design work by the recruitment of several members of the Harwell fast reactor team; and by 1957 they had designed a thermonuclear weapon. Roberts and Taylor went on to become leading physicists at Culham in the controlled thermonuclear fusion project.

The post-Suez reconciliation between the US and the UK, the apparent success of the Grapple tests and the Soviet sputnik launches in autumn 1957, all helped Harold Macmillan to persuade President Eisenhower that it would be wise to resume the wartime collaboration on nuclear weapons. For this to happen, however, the US had to amend the McMahon Act. As a step in this direction Eisenhower and Macmillan authorised on 24 October 1957 a meeting between US and UK weapon scientists which took place soon afterwards in Albuquerque. The British were instructed to discuss their designs: the Americans were there only to listen – to find out what the British had really done. Carson Mark, a Canadian member of the British mission to Los Alamos who stayed on after the war and became head of the theoretical division, told us that a US general was present to ensure that no American physicist spoke out of turn. The British made a presentation and demonstrated the fission and thermonuclear-boosted fission designs which they had tested in the Grapple series. The Americans were polite but not too interested. After a recess, according to Norris Bradbury, the Director of Los Alamos, the British demonstrated a design of an untested two-stage radiation implosion weapon. Bradbury, Mark and the other US physicists were now impressed: even though the British effort was run on a shoestring, the British had produced a novel design incorporating the Ulam-Teller concept. After their ‘Super’ experience the Americans had learnt to rely on numerical computation of their weapon designs and therefore used a cylindrical secondary, since they were able to simulate the thermonuclear process in a cylinder where propagation was effectively one-dimensional. Mark recalls, however, that the British, who had no computers at Aldermaston to speak of, unveiled a spherical secondary.

This meeting allowed the US to consider Britain not as a simple nuclear power but as one which had ‘achieved an advanced state of weapon research and development in both the fission and thermonuclear fields’ – to quote the report of the subsequent US-UK meeting of weapon scientists in Washington in August 1958. The legislation which amended the McMahon Act gave special rights to an ally (of which Britain was then the only example) who had made substantial progress in the use of nuclear energy for weapon purposes: ‘substantial’ meant knowledge of Ulam-Teller. The amending legislation was signed into US law by Eisenhower on 2 July 1958 and signified the beginning of the post-war special (and very close) relationship between the US and UK on nuclear weaponry.

The evidence is very strong that it was not until 28 April 1958 at 1905 GMT that Britain first tested a real H-bomb incorporating the Ulam-Teller concept. This was the Grapple Y test held at Christmas Island which the Times Science Correspondent referred to as ‘an important test’. Macmillan in his memoirs makes the matter clear. He told ministers on 29 May 1958 that ‘our last test (a few weeks ago) was successful. Nevertheless it is absolutely vital for us to complete this series in September. If all goes well, we shall need only two explosions; but if (as is very possible) we have a failure in the new and very special system we want to test, we shall need two more’ (our italics). Grapple Y was a test of the radiation implosion mechanism: the operational H-bomb would be tested later in 1958.

It is not clear whether politicians were told in 1957 that the Grapple tests were not really megaton tests, but by 1958 they clearly knew. When Hugh Gaitskell reprimanded Macmillan on 29 April 1958 for the unnecessary continuation of the test series ‘since we have the [hydrogen] bomb already’, Macmillan replied: ‘The Rt Hon. Gentleman says we have the bomb. If he had accepted my invitation to discuss these matters a little more intimately he would have spoken with a greater degree of responsibility.’ In other words, Gaitskell would have been told privately that we did not really have a hydrogen bomb of megaton yield after all.

On 3 July 1958, a day after the amendment to the McMahon Act, a new US-UK agreement on nuclear co-operation was signed which led to two further meetings, in August and September 1958, of British and US weapon scientists, who were now authorised to exchange information. At the August meeting the two sides exchanged written reports on the design of current and forthcoming weapons. After the successful British tests in the Grapple Z series on 2 and 11 September 1958, where two large-yield (over one megaton) thermonuclear explosions were finally achieved, one of them in the presence of US observers, actual blueprints of weapons were exchanged. Again no time was lost: this meeting began on 15 September in Albuquerque.

In parallel to the exchange of weapon designs, Bomber Command and Strategic Air Command were integrated into a single strike plan under which Bomber Command prepared the way for the US to attack the major targets. This allowed the operational nuclear yields required by the RAF to be much reduced: Blue Danube, Red Beard and a few Yellow Suns would do, at least until the new Blue Steel and Blue Streak missiles came along. The Blue Streak ballistic missile programme was cancelled in 1960 in favour of the US Skybolt missile, but the first of 57 Blue Steels with boosted fission warheads belatedly became operational in 1963 and remained in service until the end of 1970.

Another reason not to rush into H-bomb production was that after the amendment to the McMahon Act the US was willing to supply complete thermonuclear weapons to Britain (and other countries) provided they were kept under US control. W-49 warheads with a yield of 1.4 megatons were provided for the 60 Thor missiles deployed by Bomber Command from 1959. RAF Canberras in Germany were equipped in 1958-9 to carry the B-28 one-megaton thermonuclear bomb under arrangements for so-called ‘tactical’ use; the warheads would be allocated by Nato’s Supreme Commander Europe (SACEUR), an American general. Shortly afterwards, as they were replaced by more advanced aircraft in the national strategic force, Valiants of Bomber Command were also assigned to SACEUR. In 1960-61 this force was built up to three squadrons with each aircraft capable of carrying two B-28s. These Canberras and Valiants were the first British aircraft to carry real H-bombs – but under the orders of SACEUR.

Production of British thermonuclear weapons based on US designs began in earnest at Aldermaston around 1960. The first operational British two-stage radiation implosion device, Red Snow, was adopted as the warhead of the Yellow Sun Mark II bomb and entered service in 1961. This warhead was a version of the US B-28, the blueprints and material specifications of which had been handed over in September 1958. The two different names for the weapon and the misleading reference to Yellow Sun were presumably chosen to cause maximum confusion.

After the Kennedy Administration in turn cancelled the Skybolt missile which was to have been the RAF’s strategic nuclear system, Macmillan persuaded a reluctant President Kennedy at Nassau in December 1962 to provide Polaris missiles to Britain in its place. The US also furnished the blueprints, specifications and non-nuclear parts for the 200 kiloton W-58 warhead used in their own Polaris A-3 missiles.

The reports on the 1958 talks state that while the US was not interested in copying British designs, there were ‘specific developments which UK scientists have made which hold a great deal of interest for us and which might offer advantages in our weapon systems’. These advances included spherical secondaries, which allowed development of compact thermonuclear weapons, and small fission systems. Joint working groups of American and British weapon-designers were established; and these JOWOGS enabled the US to keep in contact with the development at Aldermaston of an advanced variable yield thermonuclear warhead for low-level ‘laydown’ delivery to replace Red Beard in the tactical role and to allow V-bombers to attack strategic targets at low altitude. This weapon, the WE-177, was given a wide range of yields and entered service in 1966, somewhat before its US cousin, the B-61, which for once seems to have been based on a British design rather than vice versa. WE-177 remains operational today in a tactical role as the RAF and Royal Navy‘s only remaining free-fall nuclear bomb.

If Ward had not spent those six months at Aldermaston in 1955 recent British history might well have been very different. Penney would have been left with his programme of thermonuclear-boosted weapons (Short and Purple Granites) and the high yield A-bomb fallback tested in Orange Herald and Grapple X. The Grapple series would have been declared a great success and there would have been no call for the 1958 tests since the Ulam-Teller concept would have remained unknown to Aldermaston. This could conceivably have led to an earlier signing of the 1963 treaty banning atmospheric nuclear tests.

Without a radiation implosion design to show the Americans in 1957, the McMahon Act would still have been amended but US weapon details transmitted to the UK would have been restricted to fission designs: designs of small battlefield weapons such as the Davy Crocketts advertised to Congress as the principal reason for US-UK co-operation in military nuclear matters. Britain would not have been given designs of strategic thermonuclear weapons such as the detailed blueprint for the Polaris warhead, nor would it have shared as an equal (if junior) partner in a wide range of related discussions over nuclear targeting. The special relationship in nuclear matters would not have been so special: British Forces, together with Belgian, Greek and Turkish, among others, would have had access to US nuclear weaponry in Nato but strictly under US control and supervision. Britain would still have received the prototype for a nuclear submarine reactor from the US but the exchange of weapon designs would have been much more tightly constrained by the US.

Assuming that Macmillan had nonetheless been able to persuade President Kennedy to transfer Polaris, Britain would have had to design its own warhead for the Polaris missile, using one of its own thermonuclear-boosted fission designs. This would have been expensive: boosted-fission weapons are not as compact as thermonuclear weapons of the same yield and the size of the Polaris missile could not be changed. Harold Wilson in 1964 would then have had to decide whether to spend large sums on building Polaris with far less US help or to give it up. Lawrence Freedman has written of the reasons for the decision to proceed with the programme: ‘The low cost of Polaris was an extremely influential factor … The main reason for this was the enormous American subsidy in making available information relating to the design of the submarines and warheads for Polaris.’ Without the US help on warheads it is likely that Polaris would have been cancelled, together with the TSR 2 aircraft, in the financial crisis of March 1965. No Polaris then would have meant no Trident now.

More important, the US nuclear connection makes any discussion of Franco-British co-operation on the nuclear element of a future European force very difficult. Only British nuclear information dating from before September 1958 can be discussed with the French without any danger of being challenged by the US, for after that date US information may well be involved which cannot be revealed to third parties without US consent. President de Gaulle first vetoed the British application to join the European Community on 14 January1963, less than a month after the Nassau agreement on Polaris: as he himself said, that agreement played a prominent part in his decision. Again in his discussions in June 1967 with Harold Wilson at the time of Britain’s second application to join, he asked very pointedly about Anglo-French co-operation in nuclear matters. No information could be forthcoming while the Polaris programme was under way and the second application duly lapsed. In retrospect it seems that de Gaulle was right: while Britain was (and is) so bound to the US in military matters, it could not (and cannot) pursue a common European nuclear defence policy with any conviction. As it is, the thermonuclear bluff achieved its purpose: it helped Britain to delay acknowledging its loss of power and to resist the European logic of the post-war settlement by clinging onto the skirts of its transatlantic protector for another forty years.

The principal sources for this article are:

Sakharov remembered, edited by S.D. Drell and S.P. Kapitza (American Institute of Physics, 1991). The articles by V.I. Ritus and Yu. A. Romanov describe Sakharov’s contribution to the early Soviet H-bomb programme.

‘The Development of Nuclear Weapons’ in the New Encyclopaedia Britannica, Vol. 29 (1990).

The History of the Royal Air Force by J. Rawling, P. Jackson, F.K. Mason and P. Woods (Temple Press and Aerospace Publishers, 1984).

‘William Richard Joseph Cook’ by W.G. Penney and V.H.B. Macklen in Biographical Memoirs of the Fellows of the Royal Society, Vol. 34 (1988).

Quarterly Progress Report to the Joint Committee on Atomic Energy. Part III: Weapons by the US Atomic Energy Commission (July-September 1958). This report and other similarly declassified AEC reports of the period are referred to in British, French and Chinese Nuclear Weapons by Robert Norris, Andrew Burrows and Richard Fieldhouse, which will be published shortly by Westview Press.

‘Nunca me arrependido que fiz’ (‘I’ve never been sorry about what I did’) by John Ward in Publico (Lisbon), 4 April 1992.