[LONDON] Voters in the posh London suburb of Richmond headed to the polls on Thursday in a parliamentary by-election that has turned into a mini-referendum on Brexit in a pro-EU heartland.
Liberal Democrat challenger Sarah Olney, whose centrist party wants a second referendum on Brexit, is hoping the result will send shockwaves through Downing Street as the government presses on towards the EU exit door.
Ms Olney is running against Zac Goldsmith, who held the seat for Prime Minister Theresa May's Conservative Party but quit in protest after the government backed expanding the nearby Heathrow Airport.
He is now standing as an independent candidate.
"While some people feel very strongly about Heathrow expansion, lots more people feel much more strongly about Brexit," Ms Olney told AFP during the campaign.
"That's really alarmed and upset people and they want to use this opportunity to send a message."
The Lib Dems say a shock result would force the government to think again about pursuing a so-called "hard Brexit" divorce from the European Union.
The political blog Labour List called it the "Brexit by-election".
In the June referendum on Britain's EU membership, 52 per cent nationwide voted to leave, but in Richmond, a well-heeled borough in south-west London, 69 per cent voted to remain in the bloc.
Its 82-per cent turnout, one of the highest in the UK, showed it was an issue locals felt passionate about.
The unambiguously pro-EU Lib Dems, reduced to a rump presence in parliament in the 2015 general election, are eyeing a comeback by filling the void for disgruntled "Remain" voters.
Irish rocker-turned-activist Bob Geldof, a prominent Remain campaigner, weighed into the by-election to drum up support for Ms Olney on Wednesday - despite being an old friend of Mr Goldsmith.
"We lost the battle but really the war hasn't begun," he said, calling Richmond Park the start of a "fightback" following the Brexit vote.
But he was heckled by some locals.
Ms Olney, 39, faces a tough task in beating Mr Goldsmith, who won Richmond from the Lib Dems in 2010 and retained it in the May 2015 general election with 58 per cent of the vote.
Both the Conservatives and Brexit-cheerleaders UKIP have opted out to give him a clear run, and bookmakers William Hill said Mr Goldsmith had a three in four chance of retaining the seat.
However, The Guardian newspaper reported Wednesday that it had seen Lib Dem internal data predicting Ms Olney will win 47 per cent of the vote and Goldsmith 46 per cent.
Six other candidates are standing.
Wealthy, suave and soft-spoken, 41-year-old Mr Goldsmith is Brexit royalty.
He is the son of the late tycoon financier Jimmy Goldsmith, whose high-spending Referendum Party, which called for a vote on UK-EU relations, got the anti-EU bandwagon rolling in the late 1990s.
Mr Goldsmith conducted an understated, local campaign, hoping to capitalise on personal loyalty from Richmond voters.
In an email to supporters, Mr Goldsmith admitted the vote was "extremely close".
"The choice is between keeping me as your local MP and building on our progress over the last six years, or electing someone else as your MP and putting that progress at risk," he said.
Mr Goldsmith was late to Tuesday's final public debate between the candidates, saying he had been hit by his own car and had to go home to change his shredded trousers.
The polls close at 10:00pm (2200 GMT), with the result expected from 2:00am (0200 GMT) Friday.