Hammond is now said to be in a "stable" condition following his high speed crash in a jet-powered car that is being investigated by police and health and safety officials.

A spokesman at Leeds General Infirmary said: "Doctors say Richard Hammond is making satisfactory progress. This morning he has been moved from intensive care on to a high dependency unit.

"His condition has been downgraded from ‘serious but stable’ to ‘stable’."

Family and friends, including Hammond’s co-presenters Jeremy Clarkson and James May, are keeping a bedside vigil for the 36-year-old, who suffered a "significant brain injury" in Wednesday afternoon’s accident at Elvington Airfield, near York.

May said that he had been able to have a conversation with Hammond. In a statement issued through his agent today James May said: "I’ve had a conversation with Hammond today. Not a long one, but it was a conversation.

"I want to say this: doctors are cautiously optimistic about his recovery because doctors have to be. I’m not a doctor but I am his mate and I believe that deep inside the Hammond I know is perfectly intact."

May’s words added to the growing sense of optimism outside the hospital which began when it was announced Hammond had been moved out of intensive care.

Hammond was airlifted to hospital after the 300mph jet-powered Vampire dragster he was driving veered off the runway, flipped over several times and crashed on to the grass.

Investigators are trying to establish whether BBC producers should have allowed Hammond to take the wheel of the dragster. Accident investigators want to know what training he received, and how much planning went into his unofficial attempt to break the British land-speed record on Wednesday.

If the BBC is found to have failed in its duty of care to Hammond, it could face criminal charges and potentially an unlimited fine.

BBC governors were briefed on the 280mph (450kmh) accident yesterday by Mark Thompson, the BBC Director-General. The corporation has opened an internal inquiry into the crash.