Jeremy Clarkson and James May feared Richard Hammond was dead after he crashed a car during filming for "The Grand Tour".
The pair watched in horror as the 47-year-old presenter's Rimac Concept One plunged 100ft down a hill and flipped several times before landing upside down and bursting into flames, but were relieved to find he had crawled free before the vehicle exploded and suffered no serious injuries apart from a fractured knee.
Show producer Andy Willman told the Sunday Mirror newspaper: "Jeremy and James both raced down to the scene of the crash as soon as it happened. When they saw the wreckage on fire they thought Richard was dead. It was really bad.
"They were staggered he had got out of it alive, because there was just nothing left. Everyone is so relieved. If Richard had been a few seconds slower getting out, he would have been incinerated."
Richard had just completed the famous Hemburg time-trial in Switzerland when he seemed to lose control of the vehicle.
After being taken to hospital, the presenter - who previously suffered brain injuries and almost died after an accident in 2006, and was involved in a motorbike crash earlier this year - was keen to call his wife Mindy and daughters Izzy, 16, and Willow, 13, to let them know he was OK.
Andy added: "I spoke to Richard at the hospital and although he was very shaken, he was conscious and quite lucid. He has had X-rays and a CT scan and is being kept in for observation by the doctors.
!All he said about his injuries was that his knee hurt a lot, which I'm not surprised about as it now has bolts in it and it is fractured. His only worry was about letting his wife and family know he was OK.
"He has been very lucky - it's a miracle really and certainly another one of his lives gone!"
Jeremy, 57, has described the crash as the "most frightening" thing he's ever seen.
He tweeted: "It was the biggest crash I've ever seen and the most frightening and incredibly, and thankfully, Richard seems to be mostly OK."