A south Bucks man will be running seven marathons in seven days next month to raise money for his brother’s cancer treatment.

Harrison O’ Brien, from Penn, is preparing to start his mammoth run from High Wycombe to Leeds on March 12 in a bid to raise £100,000 for a drug not available on the NHS.

Tom, 32, was diagnosed with a rare form of eye cancer, uveal melanoma, ten years ago and despite receiving the all-clear from doctors, the cancer returned in 2013.

While conventional treatments do not work on this form of cancer, a new immunotherapy drug, Ipilimumab, was initially provided to Tom on the NHS following the latest diagnosis.

However it is likely he will need a further round of treatment - which is not eligible for NHS funding.

Harrison’s gruelling challenge is the most recent in a series of fundraisers – including marathons and triathlons - undertaken by members of Tom’s family, which have so far raised £13,365.

The 25-year-old said: “I am quite excited really. Part of me is dreading it, I’ve heard some real horror stories but I am well prepared, I’ve been training for about six months. I feel fit enough.

“I’ve got friends and family running along with me, so I have at least one person running with me at a time.

“You do notice when you are training having someone with you is a big help. It can be a bit lonely.”

Tom currently lives in Hertfordshire with his wife Juliette and nine-month old daughter Amelie.

Harrison, who works for Cancer Research, added: “He is quite an inspiration for me in how he deals with it. He has a young family, a young daughter who is his absolute world.

“When it gets hard for him, if he doesn’t get good news, it’s good for him to have that distraction.

“He just keeps on going and doesn’t give up.”

For more information and to donate visit https://www.gofundme.com/7marathons7days