A technology worker donated stem cells to a stranger after joining the Anthony Nolan register a decade ago.
Konrad Peczkowicz, 26, signed up while still at school in Dagenham and only recently received the call that he may be a potential match, describing it as a "positive shock."
Mr Peczkowicz, who now lives in Barking, said: "I was told that there's a likelihood you don't get called, so it felt good that there's a chance to help."
Read more
Barking and Dagenham planning applications submitted this week
Which east London borough saw the most reported crime last month?
He described the donation process as straightforward and supportive, adding: "My donation experience was incredibly simple.
"The nurses were very kind and helped throughout the whole process. It is quite time consuming (took me 6 hours!) but I would argue it was worth it, especially given I did it around my birthday."
Mr Peczkowicz encouraged others to consider joining the register.
He said: "If you're thinking about registering, just do it. Getting that call and knowing I can make a change is a wonderful feeling."
Share