Lib Dem Sarah Olney wins Richmond Park by-election

The Lib Dems have won the by-election sparked by Zac Goldsmith's resignation over Heathrow Airport expansion.

Voters in the southwest London constituency of Richmond Park delivered a Brexit backlash against Theresa May, overturning a massive 23,000 Tory majority.

Sarah Olney won 20,510 votes, a majority of 1,872 over the pro-Brexit Mr Goldsmith, who won 18,638 votes standing as an independent.

Speaking after her win, Mrs Olney told Sky News that anti-Brexit feeling had been a major theme among voters she had spoken with during her campaign.

She added: "Most voters were saying they were really alarmed about Brexit, really alarmed about the direction it is taking the country and they want to do something about it."

During her victory speech, she said the voters had "sent a shockwave through this Conservative Brexit government and our message is clear: We do not want a hard Brexit, we do not want to be pulled out of the single market and we will not let intolerance, division and fear win".

To her rival, Mr Goldsmith, she said: "I wish you well and assure you I will continue your fight against the expansion of Heathrow."

Following his defeat, Mr Goldsmith said: "This by-election that we just had was not a political calculation, it was a promise that I made and it was a promise that I kept."

Labour's Christian Wolmar came a humiliating third with 1,515 votes, losing his deposit, in a dismal performance that will lead many of the party's MPs to question whether they should have bothered to stand.

Turnout, on a bitterly cold December day, was 53.6%, the highest in a UK mainland by-election since the Tories won Crewe and Nantwich from Labour in 2008.

While all three main candidates were opposed to Heathrow expansion, the Lib Dems were spectacularly successful in turning the by-election into a referendum on Brexit.

The constituency voted by a large majority for Remain in the EU referendum on 23 June and the Lib Dems fought a campaign that was almost entirely about the Government's Brexit strategy.

The Lib Dems sensed the opportunity for a by-election upset in Richmond Park after winning a 19.3% swing in Witney in October and slashing David Cameron's 2015 majority of 25,000 majority to just 5,700.

They flooded the constituency with senior party figures and activists. Leader Tim Farron made 10 visits and former leader Nick Clegg six.

On two weekends during the campaign the Lib Dems had 1,000 activists on the streets. The result: 150,000 door-knocks and 50,000 chats with voters.

The Lib Dems even brought in Bob Geldof, who was involved in a noisy and ill-tempered clash with Nigel Farage on the River Thames during the EU referendum campaign, to campaign for their candidate on the eve of polling day.

Their victory now ranks along previous spectacular Lib Dem by-election triumphs such as Christchurch in 1993, Winchester in 1997, Romsey in 2000 and Brent East in 2003.

This by-election was highly unusual in that for the first time since Tony Benn renounced his peerage and returned to the Commons in 1963, the governing party failed to put up a candidate.

Some Tories will question the wisdom of their party not fielding a candidate against Mr Goldsmith, although had they done so the Conservative vote would have been split and made the Lib Dems' task even easier.

UKIP did not field a candidate either. Nor did the Greens, who urged their supporters to vote Lib Dem. Many Labour voters also voted tactically for Mrs Olney.

The failure of UKIP to stand in the by-election enabled the Lib Dems to portray Mr Goldsmith as UKIP's candidate, which went down badly in a constituency that voted heavily for Remain in the EU referendum.

For Mr Goldsmith, millionaire son of the late financier Sir James Goldsmith, the defeat is a personal humiliation after his pledge to resign if Heathrow expansion was given the go-ahead.

Since winning his huge 23,000 majority over the Lib Dems at the 2015 general election, his political career has gone into a disastrous freefall.

Chosen as Tory candidate for London mayor in the election in May this year, he was not only beaten decisively but also faced fierce criticism for the tone of his campaign, which critics - including many Conservatives - claimed was racist.

He will now have to continue his campaign against Heathrow from outside Parliament and decide whether he wants to attempt to regain his old seat from the Lib Dems in the 2020 general election.