‘Derek, please, not so fast’

Ferdinand Mount

  • As I Was Going to St Ives: A Life of Derek Jackson by Simon Courtauld
    Michael Russell, 192 pp, £17.50, October 2007, ISBN 978 0 85955 311 7

In all the history of second-guessing in warfare, the Window affair is one of the most extraordinary. As early as 1934, Post Office engineers reported that passing aircraft could interfere with radio reception. Less than a year later, Robert Watson-Watt demonstrated by a simple experiment in a field outside Daventry that aircraft could be detected by radio. Radar was born. Remarkably, it was only two years after this that Lindemann demonstrated to Churchill that tinfoil strips cut to a certain length and jettisoned from a height would simulate aircraft on the enemy’s radar screen and baffle anti-aircraft batteries. Churchill, always a sucker for gadgets, loved the idea, but the scientists in charge ‘looked down their noses at the suggestion’, according to Lindemann’s protégé R.V. Jones, who had first thought of it. Partly they didn’t care to see their amazing discovery so quickly outfoxed, but also they worried what would happen if the Germans got hold of this simple device. For the next five years, no research was done on Window – as the scheme came to be known. So in the first raids of the war British bombers flew over German defences like so many flights of sitting duck.

What none of them then knew was that exactly the same thought process had occurred in Germany. A technician had suggested silver strips to Göring, who immediately saw the danger to the German defences. All papers relating to the idea were impounded and strict orders issued that it should never be mentioned again. Thus both sides had denied themselves the use of anti-radar for fear of what the other side would make of it. Each preferred to protect its own civilians from being bombed rather than its bomber crews from being shot down.

As late as spring 1942, just before the thousand-bomber raid on Cologne, Window was still being held back until its likely effects had been tested. It was at this moment, with bombers and their crews being destroyed at a horrific rate, that onto the scene charged the exotic figure of Flying Officer Derek Jackson. He had already flown 60 sorties as a navigator with 604 Squadron, resulting in 11 combats, five enemy bombers destroyed, with four more damaged. He was also a lecturer in spectroscopy at Oxford, part-owner of the News of the World, a rampant bisexual, partly Fascist and wholly outrageous in his views. Jackson was put in charge of the trials – or ‘Jackson’s Air Farce’ as they quickly came to be called.

By chucking handfuls of tinfoil out of the cockpit, he quickly discovered how much was needed to blot out the enemy radar, then, conversely, how an improved radar system could learn to detect the aircraft through the chaff. In the process he was himself shot down by an ill-informed Spitfire. By this stage it was agreed that the dangers of German bombers using Window effectively against Britain were much diminished (most German bombers were now flying against Russia), and even the sceptical Bomber Harris came round. It is estimated that Window saved about a hundred British aircraft in its first week of operation. Air Marshal Portal calculated that it might have saved the lives of the crews of 250 bombers had it been introduced four months earlier.

This was by no means the end of Jackson’s wartime achievements. Before D-Day he devised a new type of Window strip to persuade the German radar operators that two ‘invasion fleets’ were approaching the French coast some distance to the east of the actual Normandy landing. And he found in a captured Junkers 88 a detector, known to the Luftwaffe as Flensburg, which he discovered to his horror was superbly effective in locking onto Monica, the tail-warning radar issued to Bomber Command. As well as alerting British bombers to impending attack from the rear, Monica also allowed the enemy fighter to zero in. Jackson carried out a mass trial himself, flying the Junkers in pursuit of a gaggle of 71 Lancaster bombers and homing in without difficulty on each of them. That was the end of Monica. Harris had her removed and more pilots lived a little longer.

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