A British woman has saved the life of a 9/11 hero who was diagnosed with leukaemia - which was brought on by his efforts following the terror attack.
New York police officer Greg Holgerson was told that a stem cell donation was his best hope of survival.
Following a worldwide search, Sue Harrison, from Northampton, was found to be a perfect match.
The pair had been exchanging letters through Anthony Nolan, the UK blood cancer charity, following the stem cell transplant in 2014, and finally had a chance to meet earlier this month.
"She won't say it, she's very humble, but she is my hero and my family's hero," the 42-year-old told Good Morning Britain.
"If it wasn't for her I might not be here today; I might not be getting time to spend with my kids, my wife and my family."
Holgerson was off-duty when hijackers flew planes into the World Trade Center on September 11th 2001.
He rushed to help with the aftermath where he witnessed "terrible destruction".
"Everyone there was covered in dust and debris. It looked like it was snowing, it was just surreal. I was born and raised in New York and it was heartbreaking to see. There were so many innocent lives taken."
Twelve years later, he was diagnosed with blood cancer, which his doctors linked to his work in the aftermath of the attack.
After undergoing several courses of chemotherapy he went into remission but a year later the cancer returned and he was told his best hope was to find a stem cell donor.
Ms Harrison signed up to the Anthony Nolan register in the 1980s when she was in her early twenties after her mother-in-law died from leukaemia.
The 52-year-old told GMB that she had forgotten that she had even signed up and was stunned to learn when she got a call "out of the blue" confirming that she was a match.
She said it was "completely surreal" to finally meet the man she saved.
Mr Holgerson said he was "getting stronger every day" and had recently returned to work after a near four-year absence.
How to register to be a donor
People joining the register must be:
be between 16 and 30 years old
be in good health
weigh over 7st 12lbs (50kg)
have a body mass index (BMI) lower than 40
The Anthony Nolan charity says it is in need of more young men to sign up.
They produce a greater number of stem cells but currently make up just 15% of the register.
More donors from black and minority ethnic backgrounds are also needed.
There are a number of factors which mean people may not be eligible to join the register which you can see on the Anthony Nolan website.
Visit www.anthonynolan.org for more information