The orthopaedic surgeon behind the operation says the technique, which involves mixing adult stem cells with collagen gel, is “amazing”.

Andrew Kent, who is 53, said “I’ve got a good prognosis. I’m very pleased with the way things have turned out.”

This is the latest in a series of good news stories involving ethical use of adult stem cells, also known as ‘non-embryonic’ stem cells.

Using adult stem cells avoids the destruction of human embryos which occurs when using embryonic stem cells.

Mr Kent was climbing with his son in the Lake District when a boulder fell on his right leg, breaking it in five places.

Despite undergoing three operations to pin the bones back together his wound became infected and he was moved to a hospital in Chatham in Kent.

Orthopaedic surgeon Anan Shetty removed stem cells from the bone marrow in Mr Kent’s hip and then mixed them with a new collagen gel called Cartifill to make a paste which was smeared into the fractures.

The surgeons then fixed Mr Kent’s leg in a metal cage to gently squeeze the bones together.

With the cage now removed surgeon Mr Shetty said Mr Kent’s bones will have healed completely in 18 months time and “he’ll be able to go back and rock climb again”.

Faced with amputation of his leg, Mr Kent commented: “You think: ‘I don’t want to lose this foot. That would be horrendous’”.

He added: “Now I’m very pleased. I can wiggle my toes”.

The Cartifill collagen gel has been invented by a South Korean orthopaedic surgeon, Professor Seok Jung Kim, who has helped Mr Shetty to pioneer a series of procedures.

The gel holds the stem cells against the bone, where they form a new layer of cartilage.

Ten patients have been treated so far in Britain with an 80 per cent success rate.

The technique only costs a few hundred pounds – far less than alternative techniques.

Prof Kim said: “Many people who have problems with the knee injuries can get effective, low-cost treatment with this technique.”

Last year scientists also using adult stem cells, but with a different technique, heralded their development “a new age in surgical care”.

Colombian mother-of-two Claudia Castillo, who now lives in Barcelona, was told she may lose a lung after tuberculosis caused the collapse of one of the tubes connecting her windpipe to her lungs.

But a UK team of scientists in Bristol were able to help repair the tube by growing a new section in the laboratory from Miss Castillo’s own stem cells.

The cells were encouraged to develop around the bare frame of a donor windpipe. The piece was then cut to size and fitted into Miss Castillo’s own windpipe.

One of the researchers said: “This successful treatment manifestly demonstrates the potential of adult stem cells to save lives.”