British politics is on the cusp of a generational shift. To feel it, head to Milton Keynes, a city just north of London. Chris Curtis, the Labour candidate for Milton Keynes North, is relatively young at 29. So are the locals, with an average age of 37. The city as a whole is a sprightly 57. Founded by Harold Wilson’s Labour government, it was dubbed a “Los Angeles in Buckinghamshire” for its grid-patterned roads and optimistic spirit. Sitting by the watersports lake where his parents met, Mr Curtis is evangelistic about the opportunities that post-war “new towns” granted working-class families like his. Britain, he says, should build more of them.

The Labour Party’s electoral coalition is also young, to an extent remarkable in history. Britons once voted by class, but a decade ago they polarised around age. A skew to the young that started when Ed Miliband led the party (2010-15) has persisted, even as Sir Keir Starmer lifts the party’s fortunes across the board. If today’s polls were replicated at a general election, Labour would form a government with the support of 57% of voters under 24, a bigger share than any winning party since at least 1987, and possibly ever. But it would have only 30% of the over-64s, the lowest over the same period. The median Labour voter is aged 43, against 57 for the Tories, who now lag in every cohort below 65. Sir Keir boasts that Labour is the “party of working people”. In age, true enough.

For a party that wants to fix Britain’s sclerotic economic growth this is an opportunity. An expanding body of research suggests that older people’s voting behaviour can contribute to economic stagnation, a phenomenon that Tim Vlandas of St Anthony’s College, Oxford, terms “gerontonomia”. Britain has an acute case: Boris Johnson’s government was elected with the support of 64% of pensioners. It delivered a growth-stunting Brexit and gummed up the planning system. Out of the labour market and reliant on assets, the argument runs, older voters place less weight on growth, reward policies which keep inflation down and house prices up, and are less prone to punish economic mismanagement. On spending they favour health care and pensions over education.

Labour, by contrast, has the chance to “create a stable pro-growth electoral coalition”, says Dr Vlandas. It is chasing the highest productivity gains in the G7, driven by planning reforms which will see laboratories, factories and a new electricity grid sprout at speed. Housebuilding will be jigged up with existing ministerial powers to reimpose building targets, intervene with recalcitrant local authorities and dismiss appeals. A new generation of new towns is promised, and a return to national planning over piecemeal development. The goal is to replace a narrow debate about spoiled views with a soaring story of reversing national decline.

Conservative ministers have toyed with these ideas for years. The difference would be Labour’s freedom to execute them. Its electoral coalition will include more voters who will tolerate building, and fewer who will punish it. Labour voters are more likely than Tories to agree that they have a housing crisis in their area by a net of 29 points, and more supportive of large-scale house-building by a net of 16, according to polling for the Adam Smith Institute, a think-tank. They are also much more supportive of wind turbines, solar farms and pylons within sight of their homes, according to research by Public First, a consultancy. Mortgage-free homeowners, who lean Tory, tend to be more hostile than renters and mortgage-holders, who skew to Labour.

Geography helps. Rachel Reeves, Labour’s shadow chancellor of the exchequer, can be gung-ho about a proposed new nationwide network of electricity pylons, because only one of 36 constituencies affected is Labour-held and only three are prime targets. The party wants to redesignate some green-belt land for housing, which will bite hardest in rock-solid Tory shires where NIMBYism is fierce. (Of 30 constituencies that are more than three-quarters green belt, Labour holds two.) Some Labour figures think housebuilding has weakened the Tory dominance in areas such as Bicester in Oxfordshire and Worthing in Sussex. With a young coalition, new houses means new voters.

Party discipline will also help. Rishi Sunak weakened housebuilding targets after a rebellion by Tory MPs. Labour’s prospective intake are young, vetted for loyalty and will be bound by a pro-development manifesto. “There is an entire generation that has been screwed by the Tories’ failure to build new homes, and we are hopefully about to see that generation elected to parliament,” says Mr Curtis. A Labour government would also be liberated by its electorate in other ways. Tory voters cite immigration as their highest priority; for Labour voters, it comes joint fifth, according to YouGov, a pollster. Sir Keir would have room to do business with the European Union, since his voters, overwhelmingly, favour closer ties. Education is a higher priority. This will be a bewildering new world for Westminster-dwellers who project the priorities and red lines of the Tory electorate onto Britons at large.

Dance with the one that brung you

Too little disruption is a greater risk than too much. Labour worries about how fast builders can scale up work. Critics are disappointed that more radical reforms to liberalise land supply have been spurned. How many new towns will be built, and how large, is to be decided, and Sir Keir is earning a reputation for U-turns. He risks a dangerous middle path of building enough to annoy some of his coalition, but too little for the rest.

Yet Milton Keynes is a symbol of how fast fashion can change. Once a byword for mundane suburbia, it is again a mecca for architecture wonks, and the population is growing fast. Likewise, in 1967, it was possible to conjure a sprawling new town on rolling farmland by the stroke of a minister’s pen. Today, it is unthinkable. And tomorrow? The window of political possibility can widen overnight. A young electoral coalition contains opportunities for a party with the will to grasp them. ■

Read more from Bagehot, our columnist on British politics:
Scottish nationalism’s left turn (Jan 18th)
Keir Starmer, Reform UK and Britain’s populist paradox (Jan 11th)
What Britain’s Labour Party thinks of Europe (Jan 2nd)

Also: How the Bagehot column got its name