The mayoral race pits the Labour Party's Sadiq Khan against Conservative Zac Goldsmith. (AFP Photo)
Britons are voting in local and regional elections expected to deal a blow to Britain's main opposition Labour Party.
Voters are electing legislatures today in Scotland, Wales and Northern Ireland as well as choosing many English local authorities - including a new London mayor to replace Boris Johnson.
The mayoral race pits the Labour Party's Sadiq Khan against Conservative Zac Goldsmith. Pollsters and bookies make Khan the favorite to win and become the city's first Muslim mayor, after a campaign that saw Goldsmith accuse his rival of sharing platforms with extremists.
Opposition parties usually gain seats in mid-term elections as voters punish the sitting government. But Labour under left-wing leader Jeremy Corbyn is divided and beset by a controversy over anti-Semitism within its ranks.
Most results are due on Friday.