READ: Sister of tragic Jo Cox speaks on anniversary of Westminster Bridge terror attackPeter Milburn's health was rapidly failing before he was paired with "the only match in the world for me" - Aysha Lord, back in 2015.
Strict regulations mean donors and patients rarely meet face-to-face but Mr Milburn, 56, finally met Mrs Lord, 40, through the charity DKMS on Tuesday.
The pair were matched by the charity after Mr Milburn, from Marske-by-the-Sea in North Yorkshire, was diagnosed with myelodysplastic syndrome in 2015.
The grandfather of three called her his "genetic twin" when the pair met and hugged after years of swapping anonymous letters, adding: "Aysha was the only match in the world for me.
"When they said they'd found a match it was, like, the weight off my shoulders - such a relief. Speechless. Wrap her up in cotton wool, don't let anything happen to her."
A year earlier, Mrs Lord, a nurse from North Wales, had registered as a donor after seeing an appeal featuring a red-headed child who resembled her daughter.
Her blood was passed through a machine that isolates and collects stem cells before being transplanted into the patient - a process called peripheral blood stem cell collection
Visibly emotional, Mr Milburn said the transfer was "painless and it took 40 minutes".Fighting tears, he went on: "It was the best 40 minutes of my life. I think I'm a new man again.
"When I really thought I was going to die at one point I thought 'the children are going to be without a dad'. And that's what gets me every time. I can't help it."
He thanked his donor for "a few additional years to be a dad to my children, a husband to my wife and a granddad for my grandchildren".
Mrs Lord said: "Knowing that someone is going through this and you're the only thing that can help them was quite moving.
READ: Yorkshire’s £3.2bn aerotropolis plans are ‘encouraging’ and ‘innovative’, says Department for Transport"You are picked to go and help this person you don't know. I just thought if that was me or someone in my family I would want someone to help."
She encouraged others to register, saying: "All you've got to do is swab inside of your cheek and send it off and you could be somebody's life-saver.
"I will never forget when that tiny bag of my blood stem cells went out the door. I would donate again in a heartbeat."
DKMS has more than 350,000 blood stem cell donors in the UK and eight million worldwide.
More than 68,000 have received a potentially life-saving donation through the charity since 1991.
If you're generally healthy and aged between 17 and 55 you can receive home swab kits at www.dkms.org.uk.