Sadiq Khan looks set to become the new Mayor of London - boosting Labour after it slumped in Scotland's elections.
Khan, who would be the city's first Muslim mayor, was on course for victory over Conservative Zac Goldsmith, reports BBC.
The result would bolster leader Jeremy Corbyn after Labour were beaten into third in Scotland by the Tories and lost English councillors.
In Scotland, the SNP said it would form a minority government after winning its third election in a row.
First Minister Nicola Sturgeon is celebrating what she said was an "emphatic" victory, her first as party leader, after the SNP emerged as the largest party at Holyrood with 63 seats, ahead of the Conservatives on 31 and Labour on 24.
But she played down talk of another independence referendum after falling short by two seats of an overall majority.
In Wales, Labour remains as the largest party, with 29 out of 60 seats, but was denied a majority as Plaid Cymru and UKIP both made notable gains. Counting is continuing in Northern Ireland although it has been a good day so far for the DUP and Sinn Fein.
Khan's expected victory would end eight years of Conservative control of City Hall. The former Labour MP and minister, 45, would become London's third mayor after Johnson and Ken Livingstone.
Although the result has yet to be declared he got 44.2 percent of first preference votes to Mr Goldsmith's 35.6 percent - second preference votes are now being counted with Khan set to pass the crucial 50 percent mark when they are added in.
The result had been due to be announced early evening on Friday but has now been delayed, with organisers London Elects saying they are "working towards a declaration at midnight".
"The returning officer is currently updating candidates and agents. There were some small discrepancies with regard to the mayoral figures and we have to take the time to check them," a spokesman said.
--IANS
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