Video report by ITV News Correspondent Richard Pallot
Three years ago, James O'Donnell wasn't long a new dad.
When he should have been enjoying time with his wife and son, a diagnosis with a rare blood disorder threatened to tear him away from them.
Only one thing could save him - an urgent blood stem cell transplant.
With none of his siblings a match, a frantic search took place to find someone who could help. Incredibly that person was a perfect stranger, Leah McDougall, who had registered to donate her stem cells.
Now fit and healthy, this week James met his donor for the first time at a gala night for charity DKMS - the organisation which matched them in the first place.
Speaking to ITV News, James said meeting his donor was "the second greatest moment of his life".
The pair embraced on stage, joined by members of James' family thankful for her donation.
"It was surreal," said Leah.
"I don't think it has hit me properly that I have saved someone's life - but I am super grateful that I have been given the opportunity to be able help a man see his son grow up."