A man who watched helplessly from a bus as a tree fell on a moving car, killing the motorist, said “it all happened in slow motion”.

Jed Clifford, 40, was travelling to work, when he witnessed a tree of “30 or 40 feet” crush red Peugeot 307 in Lower High Street at around 6.50am today.

Police said the driver, a 50-year-old man from Harrow, was pronounced dead at the scene.

Mr Clifford said: “I was on the lower deck of the bus and I saw the tree fall. The car had just gone past the entrance to Wickes.

“He was driving away from the tree but it fell across the car. It all happened in slow motion. It was like something you’d see on one of those weird weather programmes.

“There wasn’t much traffic but the man was driving quite slowly, and the tree fell at an angle.

"I don’t think he could have avoided it even if he had floored it.

“I jumped out the bus and ran up to the car, and then thought, what am I going to do? There was someone already there on the phone to the ambulance and police.

“There were other people who were walking past who stopped to help and a builder who jumped out of his van, but the tree was too heavy to move.”

Lower High Street remains closed between Dalton Way and the Bushey Arches.