Amateur swimmer Alan Skilton has battled extraordinary odds to complete a 20-mile fundraising swim for the Exeter Leukaemia Fund (ELF) in memory of his stepson.

Alan began his fundraising challenge in March this year, aiming to swim 20 miles in 12 weeks at Okehampton's Parklands Leisure Centre pool to raise money for ELF, which supported his family after his stepson was diagnosed with an incurable form of blood cancer.

However, he tackled an unexpected obstacle after falling ill partway through the challenge, which forced him to pull out all the stops and complete the 20 miles in nine weeks instead. He has successfully completed his swim and has raised around £750 for the charity, although the final amount will not be known until the end of the month as his Just Giving page remains open until June 28. He hopes to have hit his £1,000 target by then.

Alan said of the swim: "I was ill, and that stopped me from swimming for three and a half weeks. I was off work. I was not able to swim. My 12-week challenge turned into a nine-week challenge, and I went from being able to do 70 lengths in the pool in a session to 20. It built up slowly to 30 and 40 lengths, but the most I ever got back to was 50.

"It's been fantastic. Gabrielle, my wife, has been absolutely fantastic and wonderful with her support. ELF have been very supportive and the support I've had from the lifeguards and the staff at the pool really does need to be mentioned in a big way. I had a couple of free swimming lessons to help me improve my technique."

Alan's achievement is all the more remarkable, given his own health scare. In 2010, he experienced multiple angina attacks and a heart attack, leading to the insertion of several stents. He later suffered a brain aneurysm, eventually causing blindness in his left eye. He underwent two major surgeries, which he was told he might not survive. The surgery proved successful, and the sight in his left eye is slowly returning.