Mum-of-two Claire Wilson is tackling the gruelling 26-mile event in support of the Anthony Nolan blood cancer organisation. She will be joined by friend Catherine Horsfall, from Denholme, and together they aim to raise £3,700. Accountant Mrs Wilson, 37, used to swim for England, but only took up running about two years ago.

“Catherine and her father David Portas – who is taking part too – are experienced marathon runners but it is completely new to me,” she said.

“I started training in November and am gradually building up the mileage. I’m up to about half-marathon distance now.

“It’s going OK but it is extremely tough, physically and mentally. Each training run now is over two hours, so with working full-time and being a mum to two teenage children, it’s also difficult simply fitting it in.

“But I’m determined to complete the challenge to thank Anthony Nolan for everything it has done.”

Her dad, Steve Swatman, who used to run Broomhill Post Office in Keighley with wife Glen, was diagnosed with acute lymphoblastic leukaemia in December, 2011.

He was taken ill in Spain while travelling around the world.

Mr Swatman underwent intensive chemotherapy and after several months was able to return to England, where treatment continued.

His only chance of survival was a stem cell transplant, but none of his family was a match and no other donor could initially be found.

However – thanks to the Anthony Nolan charity – a match was eventually identified, and in October 2012 Mr Swatman received lifesaving stem cells.

He is now doing well and recently met his donor, Marc Turnbull, a junior doctor at Leeds General Infirmary.

“As you can imagine that was an extremely emotional meeting,” said Mrs Wilson, an ex-pupil of the former Bronte School in Keighley, who now lives in Halifax.

“Running the marathon is a phenomenal challenge for me but I wanted to do something for the charity in recognition of all it has done.”

Mary Campbell, head of events at Anthony Nolan, said: “We are delighted that Claire and Catherine are running the marathon with us on April 26.

“The funds they raise will enable us to recruit potential bone marrow donors to the register – any one of them could be a lifesaving match for someone with blood cancer.”

To sponsor the duo, visit http://uk.virginmoneygiving.com/fundraiser-web/fundraiser/showFundraiserProfilePage.action?userUrl=Catherine-and-Claire

Visit http://www.anthonynolan.org for further information about the charity.