Parties are making a final push as voting comes to a close in a crucial by-election in Richmond Park - and voters decide whether to re-elect Zac Goldsmith following his resignation from the Conservatives.

The by-election in the south-west London seat was triggered in October following the announcement by Theresa May’s administration to expand the capacity of Heathrow airport.

Mr Goldsmith has been a vocal critic of the plans for the past decade and promised his affluent constituents he would trigger a by-election long before he was elected six years ago.

In the final hours of campaigning, the Lib Dems hit the streets with Bob Geldof, who attacked Mr Goldsmith, an old friend, for being a failure and chanted "Zac is crap" while posing for pictures. The singer joined Sarah Olney, an accountant working at the National Physical Laboratory in Teddington, who joined the Lib Dems in May 2015, to chat to voters.

Polls in the contest will close at 10pm and a Richmond council spokesperson told The Independent they expect the result of the by-election to be announced between 2 and 4am.

But while many expect Mr Goldsmith to be returned to his seat – as an independent – with his comfortable majority intact, others are less convinced. The Liberal Democrats who are making a concerted effort to retake the seat – held by them until 2010 – believe the race is much closer and that their candidate is edging closer in the polls.

In the last 24 hours the bookies’ odds have also narrowed significantly – with many losing confidence in the ability of the former London mayoral candidate to pull off a victory.

At the 2015 general election Mr Goldsmith – then under the Conservative banner – held a significant majority of 58 per cent. His closest contender, a Liberal Democrat, had just 19 per cent. However, this could have been part of a national trend experienced on the night of the election, in which Lib Dem voters left the party in their droves.

The big issue of the Richmond by-election is whether the Lib Dems’ relentless campaigning on Brexit has paid off – they have attempted to make this not a by-election on Heathrow but rather one on the Government’s plans for leaving the EU in a constituency that voted to Remain by over 70 per cent at the referendum in June.

And while Mr Goldsmith and Ms Olney appear to have the same views on a third runway at Heathrow, the referendum is quite clearly the diving line. Mr Goldsmith was a Leave campaigner while his closest rival has vowed to vote against Article 50 in the Commons if she is elected. If the Lib Dems manage to pull off a victory – as they have been spinning – it is clear the by-election will be presented as a rejection of the Government’s Brexit plans.

Nick Clegg, the former Liberal Democrat leader, who led the party to a bruising defeat at the 2015 general election, has said the by-election could stop Theresa May’s government pursuing a hard Brexit if his party’s candidate emerges successful.

Addressing supporters in the constituency last week, Mr Clegg said an extraordinary upset was within his party’s grasp, marking its return from its general election disaster – and forcing Ms May to change course dramatically on Brexit.

Mr Clegg said: “Every once in a while a by-election can have real national significance.

“In Ribble Valley it stopped the poll tax, in Crewe it ended Gordon Brown’s 10p tax hike and in Brent East it demonstrated the level of public animosity towards the Iraq War.

“This time, a Liberal Democrat victory on an unapologetically pro-European platform could cause the Government to rethink its hard Brexit agenda.”

Neither the Tories nor Ukip are fielding candidates to stand against Mr Goldsmith. Some Labour MPs urged their party to avoid contesting the by-election to give the Lib Dems a better chance of winning, but writer, broadcaster and railway historian Christian Wolmar is representing the party.

The Greens, who called for a "progressive alliance" against Mr Goldsmith, are not fielding a candidate.