At nine years old, Jan Taylor was given less than a year to live.
Born with the same kidney disorder - nephrotic syndrome - that had claimed the life of her five-year-old sister, her chances looked slim.
A transplant from a deceased donor saved her life - and that kidney lasted almost 50 years.
However, it had started to fail again.
As Jan prepared for surgery at Oxford's Churchill Hospital, her saviour this time was her husband, Mark, and a kidney-swapping scheme made possible by a law change 20 years ago.
The Living Kidney Sharing Scheme allows people who are not a match for their loved one to donate a kidney to a stranger, in return for a suitable organ for the person they wish to help.
Jan and Mark, who live in Cricklade, Wiltshire, met on a blind date in 2010, after Jan placed an advert in a national newspaper.
Mark, who was on holiday from New Zealand, responded and, as Jan puts it, "the rest as they say is history".
After 15 happy years together, the kidney Jan received in 1976 began to fail.
Without another transplant, she faced a future on dialysis.
"Mark was keen to donate" says Jan.
"He did several tests, as did I, to make sure we were fit enough for surgery, but Mark wasn't a direct match."
Despite that setback, the couple were able to join a national database of donor recipient pairs.
This was thanks to a change in the law in 2006 enabling living donors to give organs to strangers.
"We knew the paired exchange scheme was there," says Mark.
"I was actually at the hospital with Jan, having her first lot of dialysis when we got the phone call, and they told me they had found us a match."
"I was told 'just imagine I'm giving the kidney directly to Jan'," Mark adds, "but the advantage of the paired exchange scheme is that more people are getting kidneys."
Jan and Mark are part of a chain involving three couples, each donating a kidney to another person in the group.
The system, made possible under the Human Tissue Act, has now led to more than 2,000 living kidney donations across the UK.
In some cases, up to five hospitals are involved in a single chain.
All surgeries take place on the same day, partly to ensure no donor withdraws after their loved one has received a transplant.
Sanjay Sinha, a consultant transplant surgeon at the Oxford Transplant Centre, says extensive planning is required.
"The systems are set up with nurse specialists, transport organisations all in waiting," he says.
"Once the kidney comes out it's put into ice and there's a colleague waiting to transport it to another hospital where there's a patient waiting."
Four weeks after surgery, Jan and Mark are back at the Churchill Hospital for regular check ups.
Dr Paul Harden, consultant nephrologist and transplant physician at the hospital, says: "We would hope Jan will now have a much better quality of life, getting back to physical fitness and hobbies and maybe even returning to work, which would have been unimaginable has she stayed on dialysis."
Mark and Jan are now raising money for the Oxford Kidney Unit Trust, to thank the staff and acknowledge the two anonymous couples who helped make it all possible.
"It had almost got to the point where we couldn't do anything, we couldn't go anywhere, because I had no energy" says Jan.
"Then within hours my kidney function has gone from almost nothing, to better than many people's normal levels. Now we can even think about holidays."
"I'm already back at work already," adds Mark.
"The whole process is amazing, we getting our life back to what it was a few years ago and can enjoy however many years we have left together and it's a lot more now."