This has not been a good couple of weeks for Boris Johnson. First, he had to endure the loss of his bike and then the loss, in part, of his good name.

I sympathise with him greatly over the former, as a keen cyclist (just returned from a lunchtime spin through sunny Oxford as I write). His silver-grey Marin Sausalito fell victim to thieves. It was his seventh steed to do so in as many years.

A measure of his good name fell victim to Doreen Lawrence, the mother of the murdered teenager Stephen Lawrence. She as good (or as bad) as called him a racist, and her remarks became the subject of Saturday's front-page splash in that tedious rag The Guardian. The nub of her argument was that the "black community" will not back his bid to be London Mayor. "I think once people read his views, there is no way he is going to get the support of any people in the black communty," she said.

Mrs Lawrence has a personal reason to disapprove of Johnson; she was angry with his critical attitude to the Macpherson Inquiry into the Metropolitan' Police's failure to bring her son's killers to justice. But why should she, or The Guardian, assume that she has the right to speak for all black people?