Chris's father, David Mapletoft, said he had no idea his son was taking the pills. He said: "He was already slim, muscular and well built. We just think this was (for him) just another pound or two coming away from the midriff and then he would look fantastic on the beach.
"It is all speculation. We don't 100% know that because we have no idea what he was thinking. I can't think of another reason."
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.