Sadiq Khan, a Muslim opposition MP, is on course to be elected London's mayor, loosening the ruling Conservatives' hold on Britain's financial centre after a campaign marred by charges of anti-Semitism and extremism.
The fight to run the British capital has pitted the Labour Party's Khan, 45, the son of a bus driver who grew up in public housing, against Conservative Zac Goldsmith, 41, the elite-educated son of a billionaire financier.
But rather than their social backgrounds, it has been accusations of smears over Khan's Muslim faith and anti-Semitism in the Labour Party that have dominated the campaign to replace Conservative Boris Johnson as mayor of the city of 8.6 million people which is usually known for its tolerance.
Mayors of London, which is home to the City financial district, are responsible for areas such as policing, transport, housing and the environment.
London is the top prize in local elections being held across Scotland, Wales and northern England, and there was little let-up in the accusations against Khan, who has a big lead in opinion polls, as today's campaigning ran into its final hours.
During a heated parliamentary debate yesterday, British Prime Minister David Cameron accused Khan of sharing "a platform with an extremist who called for Jews to drown in the ocean".
Labour Party leader Jeremy Corbyn in turn accused the Conservatives of "smearing" Khan. He said one of the men Cameron had accused Khan of sharing a platform with had also been close to Goldsmith.
Khan, who would be London's first Muslim mayor, says he has fought extremism all his life and that he regrets sharing a stage with speakers who held "abhorrent" views.
The former human rights lawyer has also had to distance himself from Corbyn after a row over anti-Semitism.
The row has failed to dent Khan's lead in opinion polls, a situation the Labour Party would like to be replicated in today's other local and regional elections.
But in Corbyn's first electoral test since taking over the party last September, analysts say Labour could lose dozens of seats in some of its traditional strongholds.
After Corbyn expressed confidence that Labour would gain seats, his spokesperson qualified his remarks today, saying he rather wanted to say: "We're not in the business of losing seats and we'll be fighting to win as many as possible tomorrow."