|Sarah Olney, who only joined the Liberal Democrats in 2015|
Goldsmith ran as an Independent candidate, and at the 2015 general election won the Richmond constituency by a 23,000 vote majority. The Conservatives, along with UKIP and the Greens didn't field a candidate.
So, Sarah Olney is Richmond Park's new Member of Parliament, after campaigning on Heathrow but also on Brexit, using to her advantage the fact that around 70% of people in Richmond voted to remain in the European Union, whereas Goldsmith was a leave campaigner.
Olney got 20,510 votes, beating Zac Goldsmith with a majority of 1,874 with the former Conservative MP getting 18,683 votes.
Things began looking good for the Lib Dems just before 1am on Friday morning, as the ballot papers began to be counted and many on the ground started to realise how close it was between Olney and Goldsmith, just from looking at the ballots stacked on the tables.
Shortly after 1am, Lib Dem opposition leader on Richmond Council Gareth Roberts said he was "cautiously optimistic", meanwhile Labour supporters on the ground started to say they believed Olney had won by around 2,000-4,000 votes over Zac Goldsmith.
As 2am began to approach, Sky News decided to call the by-election for Olney, saying it was clear she had won.
Over the past few weeks the Lib Dems have thrown everything at this by-election, with hundreds of supporters canvassing Richmond, and key party figures joining the effort, including leader Tim Farron and former leader and Deputy Prime Minister Nick Clegg.
Sarah Olney becomes the Lib Dems ninth MP in Parliament, following the parties disastrous general election last year, in which they lost most of their seats, Olney will also be the only female Lib Dem Member of Parliament.
Richmond Park By-election facts:
Turn out of voters: 53.6%, down from 76.5% at the general election in 2015.
Labour achieved just 1,515 votes loosing their deposit.