Sadiq Khan, the son of a Pakistani bus driver, was on Saturday declared the new London mayor after he beat his nearest rival in what is being described as a landslide, marking the return of Labour rule to the UK capital after eight years.
The 45-year-old Opposition candidate takes charge as the first Muslim head of City Hall in London as counting in the so-called "Super Thursday" polls came to a close.
Khan's win seemed inevitable as all first preference votes were counted, giving him a 46 per cent vote share, nine points ahead of rival Zac Goldsmith.
It marks the return of Labour rule to the British capital after eight years of Conservatives in power.
Though it appeared mathematically impossible that Goldsmith could catch him on second preference votes, but the count had to officially go into second preference votes to cover the 50 per cent vote share required for a clear victory.
Labour leader Jeremy Corbyn tweeted his congratulations to Khan way before the formal announcement: "Can't wait to work with you to create a London that is fair for all! #YesWeKhan."
It is believed that the high turnout helped Khan after 45 per cent of Londoners came out to vote yesterday and he bagged an estimated 1.1 million votes.
Khan is a former human rights lawyer and an MP from Tooting, east London, since 2005. A prominent figure in former Labour Prime Minister Gordon Brown's Cabinet, he resigned from the shadow Cabinet last year to launch his campaign to replace Boris Johnson whose second and final term ended on Friday.
Khan relied mainly on his solid working class roots and upbringing on a London council housing estate as strong credentials against Goldsmith's more privileged background.
Oxford-educated Goldsmith, the son of late billionaire Sir James Goldsmith and brother of Jemima Khan, trailed through most of the mayoral campaign attributed by some to his camp's failed attempts to link Khan with extremist personalities.
Jemima, ex-wife of Pakistani cricketer-turned-politician Imran Khan, tweeted as the results became clear: "Sad that Zac's campaign did not reflect who I know him to be- an eco friendly, independent-minded politician with integrity."
Voters were able to register their first and second preferences for mayor, and two types of London Assembly member one for their area and one for the city.
The new mayor has control over four major policy areas in London - transport, policing, environment, and housing and planning under the London Assembly's scrutiny.