Billionaire Richard Branson said he thought he was going to die after crashing head first onto the road while training for a fundraising adventure .

He was cycling downhill at the British Virgin Islands with his two children, Holly and Sam, when he hit a hump in the dark, he wrote in a blog post.

"The next thing I knew, I was being hurled over the handlebars and my life was literally flashing before my eyes," said the 66-year-old founder of the Virgin Group .

"I really thought I was going to die."

He flew head first onto the concrete road, but his shoulder and cheek "took the brunt of the impact".

He suffered torn ligaments and a cracked cheek, and has to drink using a straw. He also had severe cuts on his body.

He was wearing a helmet, which he said saved his life.

His bicycle disappeared over a cliff. He has since recovered it, and it was "crumpled" and "completely destroyed".

"I really couldn't believe I was alive, let alone not paralysed," he wrote.

When his assistant Helen Clarke arrived on the scene, he said he joked with her: "I'm alive! At least you've still got a job!"

Mr Branson is known for his record-breaking adventures like trying to circumnavigate the globe in a balloon, and kite-surfing across the English Channel in world record time.

He said of the cycling mishap: "My attitude has always been, if you fall flat on your face, at least you're moving forward.

"All you have to do is get back up and try again. At least I'm practising what I preach - though a little too literally!"