Hitting the wall is a tough test for any runner - but when Dave Brown and Mark Raphael put themselves through the pain barrier at the Belfast Half Marathon, they had a special motivation to reach the finish line.
Dave and Mark completed the 13.1-mile challenge in support of their friend Jonathan Hamilton, who suffers from multiple sclerosis and recently underwent ground-breaking stem cell treatment at Hammersmith Hospital.
"Jonathan has had a challenging time as his condition has progressed," said Dave. "He has been in and out of hospital for consultations, treatment and recovery. Throughout this time he has spent extended periods away from home, his loved ones and his boys, Freddie and Harry."
Jonathan's condition affects his central nervous system. He has mobility problems and walks with to straighten his gait. He also suffers from poor vision, caused by damaged nerves in his brain and spinal cord.
Thanks to the outstanding care of experts at Hammersmith Hospital's haematology department, Jonathan is showing signs of improvement after undergoing stem cell therapy. He finds it easier to walk, is less fatigued and is more alert generally.
One of only a few dozen patients to have received a haemaopoietic stem cell transplant (HSCT) at Hammersmith, Jonathan is among the first to benefit from the new treatment.
The procedure involved transplanting a special type of stem cell extracted from Jonathan's own blood back into his body while his immune system was suppressed using chemotherapy.
Mark added: "Time will tell how successful this has been but the signs are positive. He is enjoying spending time with his family and he is growing stronger by the day."
To show their appreciation for the team which is helping Jonathan manage his condition, Dave and Mark set out to support The Blood Fund. The pair raised more than £5,000, breaking their own personal best times.
Their contribution will help fund pioneering research at Hammersmith as well as improvements to the hospital environment for patients with blood disorders.
Inspired by Dave and Mark's story? Find out more about our exciting fundraising opportunities at www.imperialcharity.org.uk/fundraising-events