Jeremy Clarkson says Hammond's crash during a mountain race was the "biggest" and "most frightening" he had ever seen.
Former Top Gear star Richard Hammond has been airlifted to hospital after escaping a "serious" car crash.
The presenter was involved in the accident at a Swiss mountain race while filming for his TV show.
The 47-year-old suffered a fractured knee while racing an electric super car, but was not seriously injured.
Hammond's friend and fellow presenter Jeremy Clarkson described it as the "biggest" and "most frightening" crash he had ever seen, adding in a Twitter post: "Thankfully, Richard seems to be mostly OK."
A spokesperson for The Grand Tour said: "Richard was conscious and talking, and climbed out of the car himself before the vehicle burst into flames.
"He was flown by air ambulance to hospital in St Gallen to be checked over - revealing a fracture to his knee.
"Nobody else was in the car or involved in the accident, and we'd like to thank the paramedics on site for their swift response.
"The cause of the crash is unknown and is being investigated."