Two women and an 11-year-old boy are still in hospital after colliding with a bus on Charing Cross Road.
A 47-year-old woman is critically ill.
An 18-year-old woman is in a serious condition, but stable and the boy is also said to be stable.
All three were pedestrians.
An investigation is under way but no arrests have been made.
More top news
His top speed is believed to be the highest ever recorded in the UK by a rider carrying a pillion passenger.
The mayor took time out from City Hall to join Conservative party workers handing out leaflets in Uxbridge and South Ruislip.
No matter where you look, London's population is getting older - with the exception of one of the capital's boroughs.