The excitement of the Gardella family was palpable as they waited in the arrivals hall at Birmingham Airport for someone they'd never met before but who already meant so much to them.
Finally, they spotted a middle-aged woman wearing an oversized hoodie amongst the passengers arriving from Dusseldorf.
The family instantly recognised Dana Ernst-Behme from her WhatsApp picture and nine-year-old Sofia Gardella took the lead, eagerly approaching their guest and flinging her small arms around her neck. The hug was a long one and Ms Ernst-Behme closed her eyes as she embraced her young host.
This meeting was so special because it was the first time Ms Ernst-Behme met the girl whose life she had likely saved.
Sofia, from Mansfield, Nottinghamshire, was just two years old when her family discovered she urgently needed a stem cell transplant. She was diagnosed with Congenital Amegakaryocytic Thrombocytopenia (CAMT), a condition that is so rare doctors believe fewer than 100 people in the world have it.
CAMT causes the body to produce a dangerously low number of bone marrow cells, specifically the type needed to make platelets that clot the blood.
Sofia's medical team scoured the Anthony Nolan stem cell register and found a good genetic match with Ms Ernst-Behme, 52, from Helpsen, Germany. She donated her stem cells from her hometown and they were immediately flown to the UK for Sofia's life-saving treatment.
Sofia's mum Claire Gardella said: "I actually saw the cells arrive at the hospital. I was looking out of the window and saw the courier pull up with the box.
"It looked like a bag of blood, but obviously it was a bag of magic cells. That's what we called it when we explained it to Sofia - a bag of magic."
Ms Ernst-Behme's healthy stem cells replaced Sofia's damaged ones, and she has now made a full recovery.
After five years of emails, calls and letters with Mrs Gardella, Ms Ernst-Behme decided to visit the UK for the first time and see the family whose lives she's changed.
Read more from Sky News:
'Unprecedented' rise in people infected with diarrhoea-causing parasite
Meta 'intentionally addicts' children to social media, lawsuit claims
Just 22 minutes moderate exercise a day can offset negative effects of sitting down, study finds
'She saved my life'
Sofia said she was excited to meet her donor.
"I think it's really important [for her to visit] because she saved my life."
Sofia wasn't remotely shy around Mrs Ernst-Behme. When they got home from the airport she expertly demonstrated how to play the card game Boggle.
Mrs Ernst-Behme admitted she'd known to expect Sofia's confidence thanks to her mother's emails.
"Claire wrote that Sofia's a chatterbox and she said I [must have] had it in my bone marrow. But I said I'm not a chatterbox and then my husband said… I am," she laughed.
'We need more people to register and everyone can help maybe'
Sofia said she didn't understand what was going on when she received her bone marrow transplant because she was too young, but now she realises a stranger donated exactly what she needed to lead a healthy, happy life. She's very grateful.
Sofia said she now loves dancing, swimming and riding her bike - all made possible by the transplant she received.
Her mother said it was such a huge relief when they got the news the doctors had found a match for Sofia.
"Oh it's amazing just to think that there's somebody out there who's willing to help us, somebody that doesn't know us," said Mrs Gardella.
"We need more people to register and everyone can help maybe. There's one match all over the world," said Mrs Ernst-Behme.
Call for donors
The Anthony Nolan charity has been helping patients for almost 50 years.
It has the UK's biggest stem cell register, but desperately needs more people to sign up, particularly donors between the age of 16-25 years old. Donors under the age of 30 lead to better survival rates for patients but fewer and fewer are coming forward.
"It's really simple to sign up [to the register]," said Rowena Bentley, a spokesperson for the charity.
"You receive a swab in the post and you just need to swap your cheeks and send them back to Antony Nolan. We test those for your unique genetic type and then you sit on the register ready to be a match for a patient in need."