Despite Labour’s troubles, recent polling by YouGov showed the party still commands a national lead among the under-40s. Among men it’s by a single point, within the margin of error, but among younger women it rises to 15 points – astonishing given the Tories currently lead by as much as twenty points nationally. That should offer some succour to the team around Jeremy Corbyn, and is likely to confirm the experiences of his supporters in conversations with friends or canvassing for the party. But it is also, in the context of electoral success, relatively meaningless. Older voters decide who wins.

‘Millennials’ – the large cohort born between 1980 and the mid-1990s – favoured Remain over Brexit, and Scottish independence over staying in the union. They shifted towards Ed Miliband in the 2015 general election, and view only the Greens more favourably than Labour under Corbyn. (In the US, they preferred Bernie Sanders to Hillary Clinton, and Clinton to Donald Trump.) They are, in short, unaccustomed to winning. (Obama's victories were an exception.)

In Britain, as in America, changing demographics map on to an unfavourable electoral geography. The population of large city centres in England and Wales more than doubled between 2001 and 2011, with the number of residents aged between 20 and 29 nearly tripling – this group now accounts for half of city centre residents.

In May 2015, amid a sea of blue, England’s great cities – London, Manchester, Liverpool, Birmingham and Leeds – all voted Labour. A year later, the London mayoral race saw Sadiq Khan succeed in the face of a racist campaign which at a national level would probably have prevailed. The same day, Bristol elected Marvin Rees, the son of Jamaican and British parents, as its mayor. Both events were at odds with the story that Lynton Crosby – so expert in leveraging perceived cultural difference – wants us to believe about the kind of country Britain is.

The reason for the divergence has nothing to do with a fabled ‘metropolitan elite’ and everything to do with demographics. As well as more younger people, cities have large BME communities. This makes them more likely to have progressive attitudes on migration and be less likely to vote Tory. They still have economic worries – Islington has very high levels of child poverty – but they are less likely to blame the poor for their problems.

Britain’s electoral system, however, means that this concentration of progressive thinking in urban areas is bad for Labour. Nowhere was this clearer than in another recent poll, which showed the Tories finishing first in Wales. Labour hasn’t offered the country a meaningful answer to post-industrial decline, but the main reason this historically left-wing nation is turning blue is that it is getting older, while younger voters converge in Cardiff or move to England. Labour held on in the local elections last week, but the structural shift would appear to be unfavourable for them as the years go by.

Labour is therefore doomed under the current system unless it can appeal to older voters. In an economy set up for them, from inflated house prices to relatively generous public pensions, that could prove difficult – especially given they are more likely to their news from the right-wing press. But a crisis of geriatric care is looming, with an increasingly under-funded NHS and local services struggling to cope with the needs of an older population (the number of over-65s will rise to 15 million by 2030 from 11 million today). For Labour, the pitch should be simple: the market – and its champions in the Conservative Party – will not look after you. This has the added benefit of being true.