Having decided to freeze fares – one of only two sources of funds over which he has direct control – he had no choice but to rely heavily on the other one, council tax.

In 2021-22 Londoners had to swallow a 9.5 per cent increase in council tax, the biggest rise in England (City Hall says he was forced to make the increase “due to lack of Government funding for London’s key public services”). For that sort of money, taxpayers are entitled to expect results, but the number of affordable homes completed under him trails well behind Johnson’s record.

Johnson completed 62,387 affordable homes in his first five years as mayor, while Khan has managed 34,659 in the same period.

Work had started on another 23,000 homes in Khan’s first five years, but his target was to have 116,000 homes completed or underway by 2023, helped by a £4.82 billion grant from Theresa May’s government in 2018. And a vote-winning pledge to make 50 per cent of all homes on any new development affordable was quietly dropped for a 35 per cent target that he hoped builders would voluntarily agree to. Khan’s spokesman said he had supported a “renaissance in municipal homebuilding” by backing councils to build houses “at a scale unseen since the Seventies”.

There have been some successes. Mr Khan brought in a night Tube and improved the capital’s air quality through low-emission buses and electric taxis, and even Johnson’s most ardent supporters would admit he, too, presided over some costly failures, such as the doomed garden bridge over the Thames which cost £43m of public money before it was abandoned.

Khan has also won praise for his honesty over his struggles with mental health. He has described his “melancholy” during the pandemic and how lockdown left him feeling “really down”. He said he had “never felt suicidal” but said he suffered from depression, which led to questions from Conservative members of the London Assembly about whether he should have stepped aside “because of my mental ill-health”.

His aim, he said, in talking about his difficulties, was to help destigmatise mental health problems and show that “even somebody who may on some days not have the best mental health can still be a great mayor”.

Mr Khan won a second mayoral term in a delayed election last year. He has proved to his party that he can win at the polls. Yet the belief that Khan wants to become Labour leader has caused tensions within the party. 

Sir Keir Starmer’s allies are concerned that obvious jockeying for position by Khan and Andy Burnham, mayor of Greater Manchester, will undermine the leader by creating a perception that his own party expects him to lose the next election.

There is a growing belief that Burnham, whose “King of the North” shtick is a turn-off for many voters, may already have overplayed his hand. If Khan is to beat him in the race to become the next Labour leader, he will need to have more to show for eight years in City Hall than a legacy of making London a worse place.