Sadiq Khan made history as London’s first Muslim mayor tonight, but his victory has been overshadowed by David Cameron’s refusal to back down in a row over his links to extremists, writes Gordon Rayner, Chief Reporter.

Mr Khan, a former Labour cabinet minister, became Britain’s most powerful Muslim politician when he defeated the Conservative candidate Zac Goldsmith by a landslide. He gained more than 1.1 million votes, the single largest mandate for any individual politician in British history.

The Conservatives’ tactic of accusing Mr Khan of “legitimising” extremist views failed to win over voters in the capital, and was described as a “vile smear” by the Labour leader Jeremy Corbyn.

Several senior Tories expressed dismay at the “outrageous” and “appalling” strategy, while Mr Goldsmith’s own sister Jemima Khan said she was “sad” that his campaign did not “reflect who I know him to be”.

However Downing Street made it clear David Cameron would not be withdrawing his criticisms, suggesting the Tories may plan to use Mr Khan’s controversial past in future attempts to undermine him.

A Downing Street source said: “We don't back away from the questions we raised during the campaign.”

Mr Khan’s election received a hostile response from some in the US, where the influential Drudge Report website described him as the “First Muslim Mayor Of Londonistan” and he was called “an Islamist” by one major TV network.