Somewhere in London is my perfect match. He is well-built, a year older than me, popular with my friends and family – a real hero. We've never met.
He is my stem cell donor, a 10/10 fit for my blood tissue type, according to our human leukocyte antigen (HLA) – the unique "barcode" we each have on our immune system's cells – which allows the body to distinguish itself from foreign bodies so it can fight invading organisms.
When I was diagnosed with high-risk leukaemia last February, I was told that I would need a stem cell transplant. My bone marrow could not be trusted to produce cells on its own – the entire system needed to be wiped out, deleted with high-dose chemotherapy and radiation, and essentially replaced with a new hard drive. Without a transplant of someone else's cells, my doctor said, there was a 60% chance that the leukaemia would return, and probably kill me.
After my sister was tested and found incompatible (siblings are a match in only about 30% of cases), the hospital started searching the Anthony Nolan charity's bone marrow register for a donor. I was lucky – a month later, I was told that a match had been found: a 24-year-old "chunky lad".
Apart from his age and robust physique, I don't know anything about him. In two years' time, as long as I'm still in remission, I'll be allowed to meet him – if he agrees. Until then, donors and recipients can only exchange short, anonymous messages. But in the meantime, I can't help feeling curious about this total stranger whose blood is now flowing through my veins, whose DNA and blood group I now share (along with his Y chromosomes).
Hannah Watterson, 31, originally from County Armagh in Northern Ireland, has been wondering about her donor for years – and she is about to meet him for the first time. "I'm nervous," she says. "I feel like I should know him, because he's a part of me." Diagnosed with Hodgkin's lymphoma in 2003, Watterson underwent several years of chemotherapy. But after a relapse in 2007, doctors warned her that a stem cell transplant was her only chance of survival. "I'd already had as much chemo as they could give me. If I didn't have the transplant, I would die."
Her brother was not a match, but fortunately someone else was – Gil Lewis, now 43, a warehouse supervisor in Coventry. Lewis had been on the register for 20 years, after signing up when a friend was diagnosed with blood cancer. When he received a call one day from Anthony Nolan, inviting him to a clinic in Harley Street, London, he did not hesitate. The process of drilling into his bone to harvest the stem cells from his marrow was, he says, "totally painless" – the only side effect was some minor backache. He even ran the London Marathon six months later, in aid of Anthony Nolan.
Stem cells are frequently in the headlines, hailed as a miracle cure of the future. For many, they exist in a faraway land of test tubes and laboratories – but they are already used in hospitals, and are easily obtained from donors through a simple procedure, similar to giving blood.
It is something Mick Davidson, 58, from Northumberland, knows all about. As a taxi driver, he makes frequent hospital trips, carrying precious cargo: some of his passengers are volunteer couriers for Anthony Nolan, delivering bags of stem cells. Ensuring they arrive on time is critical, as they must be administered within 72 hours of donation. But then, Mick has known about the life-saving impact of stem cells for a long time, having donated his own 20 years ago to someone on the other side of the world.
"At the time, all we knew was that he was a young man from North America," says Davidson, who signed up to the register after his aunt died of leukaemia. The recipient of his cells was Rob Kaufman, then a 23-year-old from Ohio who had from aplastic anaemia. One day Davidson received a letter thanking him for his act of generosity, to which he replied, beginning an anonymous correspondence. "It snowballed from there, really." He first met Kaufman a couple of years later, and the pair have been close friends ever since, sharing family holidays and celebrating milestones together – Davidson attended Kaufman's wedding in 1999, and last summer their families met in Florida to celebrate the 20th anniversary of the transplant.
For approximately 1,800 people in the UK every year suffering from aggressive blood cancers and other haematological diseases, a stem cell transplant is their only hope of a cure. But despite increases in donors on bone marrow registers, the NHS Stem Cell Strategic Forum reports that more than 400 patients a year are denied treatment simply because there is no match.
Anthony Nolan, which is this year celebrating 40 years since its foundation, is calling for more people to sign up in the hope that one day they can provide matches for all. There is a particularly urgent need for more donors from ethnic minorities, who are seriously under-represented on the register, meaning that patients from these backgrounds only have a 40% chance of finding a match.
Davidson says that donating his stem cells was the most rewarding decision he has ever made, and he would encourage others to sign up to be potential donors. "It could save someone's life. And it could even change your life as well. It's certainly changed ours."
• Find out more at anthonynolan.org/bethecure.
