When Boris Johnson swept Ken Livingstone out of London’s City Hall two months ago, the Tory leadership did not know whether to laugh or cry. Should they celebrate another dagger to the heart of Gordon Brown’s prime ministership or hide behind the sofa waiting for disaster to strike? The sofa option suddenly looks attractive.

For Mr Johnson to lose his deputy chief of staff was careless enough. James McGrath made some comments that were wrongly judged to be racist and he was sacked. Either the mayor panicked or was ordered to act by Conservative Central Office. It was a mistake because it encouraged his enemies to search out their next victim – not too difficult because rumours were already circulating that Ray Lewis, the deputy mayor, had a “colourful past” involving alleged sexual and financial improprieties. Certainly the appointment was bold and the sort of thing that an Old Etonian Tory should be doing in multi-ethnic London. But it seems catastrophically careless not to have found out more about Mr Lewis before giving him the job.

The final straw was a disastrous press conference held with the mayor on Thursday when Mr Lewis claimed, falsely, to be a magistrate. This does not mean that Mr Johnson’s mayoralty is doomed but he should worry that the feline Mr Livingstone is expressing sympathy. Boris’s time in office was always going to be tumultous but few expected it to be this rocky so soon.