“In Hertford, Hereford and Hampshire,” Eliza Doolittle observed in My Fair Lady, “hurricanes hardly ever happen”. Meteorologically and electorally, the flower girl was right. These well-heeled counties of England rarely surprise: in winter and summer it merely rains, and in elections they vote Conservative.

Yet across such true blue areas, the “yellow peril” is back. The Liberal Democrats have long vied with the Tories in upscale commuter and university towns. Now, thanks to the recomposition of the electorate along Brexit lines, swaths of the old Tory heartlands are set to abandon traditional political allegiances.

St Albans in Hertfordshire is the sort of place the Lib Dems believe they can win. Just north of London, it is home to the “quite rich” voters that Tory strategists yearn for. In a national version of the board game Monopoly, St Albans replaced Mayfair in the prime spot. It is a place where married couples go for more bedrooms and green fields; the sort of place, in fact, where people tend to become Tories.

But person after person I speak to there registers their disgust at Brexit — a clear majority voted for Remain in 2016 — and the rightward shift of the Tories. Many inhabitants are London exiles, bringing with them liberal metropolitan sensibilities. St Albans may once have been a Labour marginal, but the party’s equivocation on Brexit could well have scuppered its aspirations.

The Lib Dem prospective parliamentary candidate, Daisy Cooper, is a typical resident. She commutes daily into the capital to work for a political charity. At the last election, she grew the yellow vote by 14 per cent and halved the Tory majority. After Lib Dem gains at the last local elections, she is hopeful of making it to Westminster next time.

“I stood to be our candidate in St Albans because it is exactly the sort of seat that should and could be a Lib Dem heartland, people here hold fundamentally open liberal values,” she explains over coffee. “I want to put a stake in the ground for the party and the country’s future and I absolutely think we can win.”

Ms Cooper acknowledges that the “Tory voting tradition” may be tough to overcome — some residents think that the incumbent MP Anne Main was returned on the back of a residual loyalty outside the city centre. But she now senses a “very strong desire to Remain” across the seat, intensified by Ms Main’s role in the European Research Group of Brexiter MPs.

“St Albans voted 63 per cent Remain but she continues to push for the hardest most reckless version of Brexit,” Ms Cooper says. “Local residents tell me that her position on Brexit in 2016 was a ‘wake up moment’ for them and they now realise that her values are out of kilter with theirs on a whole range of issues.”

With an energetic new leader in Jo Swinson, and a general election on the horizon for this autumn, the Lib Dems are confident that parts of Tory England are again in their grasp. The threat to the Conservatives is palpable. By chasing Brexit-backing Labour voters, the party is risking undoing its core voting coalition — losing the keys to a majority today and threatening its long-term future.

“We are facing twin threats: the Lib Dems and the Brexit party, just as grave as each other,” said one MP worried about losing their seat. “We need to focus on keeping the support of young, aspirational families in the south-east — this is the future of our party.” But if St Albans is anything to go by, it could well be too late.

The Lib Dems, however, do have a history of hubris. In 2010 then leader Nick Clegg was surfing a wave of “Cleggmania” and the party was talking of forming the next government. Then Britain’s electoral system made it suffer. So while strategists talk of winning anywhere between 75 and 200 seats, it is worth remembering that British voters can be fickle customers.

The biggest challenge for the Lib Dems may be apathy. One Financial Times colleague who lives in St Albans recalls surprise when Ms Cooper didn’t win in 2017, blaming under-motivated centrist voters. Today, however, they have many reasons to vote — Jeremy Corbyn, Boris Johnson, Brexit. Liberal England is undergoing a revival. The yellow bird is taking flight.

sebastian.payne@ft.com

Copyright The Financial Times Limited . All rights reserved. Please don't copy articles from FT.com and redistribute by email or post to the web.