A 42-year-old British man who has beaten cancer twice recently met the anonymous German stem cell donor who saved his life. Mark Ritson, a company director from Sheffield in the north of England, was diagnosed with severe aplastic anaemia in 2009, meaning his body did not produce enough new blood cells. At the time, the Anthony Nolan stem cell register searched worldwide for a donor to provide Mark with new stem cells which could cure him, but without success. Although an alternative treatment worked temporarily, two years later a relapse forced him to return to hospital. ‘This time the doctors said…