Doug Gibson donated his kidney to his 51-year-old son, also called Doug, in a four-hour operation two months ago.

The two are returning to hospital on Monday for a check-up.

Doug senior, from Gerrards Cross in Buckinghamshire, was determined to donate his kidney despite initial opposition from doctors and his son.

They thought he was too old to survive the operation, but tests showed he was exceptionally fit.

Usually doctors do not take organs from anyone over 65.

The British Organ Donor Society says the oldest British organ donor it has heard of until now is a 75-year-old kidney donor.

However, tissue transplants have been done on much older people.

Heart attack

Doug, who was forced to retire in 1978 after suffering a heart attack, insisted that he wanted to help his son.

"He's my son. It's as simple as that," he said. "It's the greatest thing to happen to a man, to get his kids out of trouble like this."

Doug junior was diagnosed with kidney failure in 1996 and was put on dialysis three days a week.

Doug Gibson junior: father's donation 'takes a lot of beating'

The process involves being hooked up to a machine five hours a day which does the kidneys' job of cleaning toxins out of the blood.

Doug junior, who has four children and one grandchild, said he had felt "Why me?" when he was diagnosed, but had been told by doctors that there was no particular reason for kidney failure.

A year ago, his father first suggested donating one of his kidneys. A person can live normally with just one kidney.

"I told him to go away, or words to that effect," said Doug junior.

But his father was insistent and Doug junior eventually gave in.

In very good nick

Bob Johnson, the surgeon at the Manchester Royal Infirmary who performed the operation, was also sceptical at first, but Doug senior convinced him to go ahead with tests at an Oxford hospital.

These measured everything from blood group compatibility to remnants of heart disease. Doug senior passed the tests easily.

Mr Johnson said: "He is in very good nick. For instance his arteries are remarkably well preserved - they are more like a 60 year old's than a 77 year old."

The operation went ahead in October and Doug senior was out of hospital in five days.

His son was out in 10 days, but had to return to hospital because of a minor problem in a tube connecting his new kidney with his bladder.

Mr Johnson said the operation went very well and says he would not be surprised to see older donors in future if people are fit.

But he said it was much safer to use younger people.

"The message from this case is the critical shortage of organs available for transplant from the living rather than cadavers," he said.