Votes are being counted in Lewisham East where Janet Daby is expected to become Labour's newest MP.
Only a third of eligible voters cast their ballot in the by-election triggered by former Labour MP Heidi Alexander's decision to quit Westminster to take up a job with London mayor Sadiq Khan.
Ms Alexander had a massive majority of 21,213 in the south-east London constituency at the 2017 general election.
The Conservatives finished second in 2017 with the Liberal Democrats a distant third.
But Lib Dem leader Sir Vince Cable has campaigned in the seat and party insiders expect an improved performance in a constituency which voted heavily to Remain in the European Union.
A Liberal Democrat source said he was "relatively confident" of leapfrogging the Conservatives and securing second place.
The official turnout has been announced by officials as 33.4% - well below the 69% who voted in the 2017 general election.
The full list of candidates is:
- Rosamund Adoo-Kissi-Debrah - Green Party
- Ross Archer - Conservative
- Charles Carey - no description
- Janet Daby - Labour
- Massimo DiMambro - Democrats and Veterans Party
- Sean Finch - Libertarian Party
- Patrick Gray - Radical Party
- Thomas Hall - Young People's Party
- Howling Laud Hope - Monster Raving Loony Party
- David Kurten - Ukip
- Maureen Martin - Christian Peoples Alliance
- Mandu Reid - Women's Equality Party
- Lucy Salek - Liberal Democrats
- Anne Marie Waters - For Britain Movement