Stephen Colman and Philip Walters have not known each other for long. But their connection runs deeper than that of the closest of friends.

For less than two months ago, Mr Colman donated a kidney to Mr Walters for a successful transplant at the Royal Free in Hampstead. The donor has since participated in a Norwood bike ride, pedalling 60 miles from London to Brighton.

Now the pair, brought together by Israeli charity Matnat Chaim, want to encourage more people to consider "altruistic" kidney donation. It is common for donors to be family members or close friends.

"For me it was three-hour keyhole surgery," said Mr Colman, 64, a mortgage broker and Golders Green Beth Hamedrash congregant.

"I went in on a Wednesday, came back Friday and was in shul on Shabbat morning. The recovery is meant to take six weeks - I took three days off."

Mr Walters, 68, a retired catering business owner from Southend, said that "over many years, my kidneys have been going down the tubes. Last October, my specialist said I would either need a transplant in 12 months, or dialysis. My wife found Matnat Chaim and, incredibly, they said they might have a kidney for me."

The Southend and Westcliff Hebrew Congregation member added that he initially felt awkward about meeting his donor, but Mr Colman put him at ease. "He is the most wonderful person.

"After the operation, he came to see me in hospital and said: 'I've just come to visit my kidney.' It was a nice way of breaking the ice."

For Mr Colman, "it was nice, knowing this was someone who needed a kidney badly and that I could help him. "You only use a quarter of one kidney, so you can spare the other. There is a Jewish saying: 'One person is gaining, the other person is not losing.'"

Although "even my kids thought I was mad", he considered it "a donation like any other I have ever made. "I want people to know that this doesn't affect your life. It really is a no-brainer."

Their pairing is a UK first for Matnat Chaim, a non-profit organisation which in eight years has found 320 matches in Israel. It is looking to expand its work globally.

"We want people to know that the risks are little and the gain is so great," said UK director Judith Abrahams. "Even if you take a kidney away, you have three or four times the amount of the reserve energy you need left.

"Some people are afraid of the operation. But long-term studies indicate that kidney donors have the longevity of everyone else. In fact, theirs is slightly higher because they are checked out so thoroughly."

Meanwhile, Mr Colman feels that he has gained a friend. "Philip is someone I would have never come across," he reflected. "But he is a lovely fellow. And besides, we have something in common."