A High Wycombe man will walk a mammoth 100k to raise money for MS Society (multiple sclerosis) which he says has helped his stepdaughter with the chronic condition which has left her paralysed on her right side.

Martin Clark, 50, is planning to walk from London’s Putney Bridge to Henley-on-Thames on September 10 and 11 to raise £1,500 for the charity, after his stepdaughter Sarah Witney, 45, was diagnosed with MS in 2004.

She also suffers from the rare progressive multifocal leukoencephalopathy (PML) condition which, according to Mr Clark, causes “irreparable” damage to the brain and can lead to disability or even death.

He told the Bucks Free Press things got so bad last year, at one point he and wife Dawn thought they were going to lose Sarah.

He said: “She fought back, regaining her speech and memory but it has left a toll on her as her brain has been left slightly damaged and she is unable to use her right leg and arm.

“Throughout all of this, I have wondered what else I can do apart from be there and support her through this journey.”

Mr Clark signed up for the Thames Path Challenge last November after seeing it on the MS Society website, and has clocked up 600 miles in training since.

He also chose the 100k challenge over the 25k and 50k also on offer.

He added: “She will always have PML which there is no cure for, but research is continuing for MS which she will also always have, so I have decided to take on the 100k Thames Path Challenge.

“I want to do what I can – she is very pleased I am doing it for her.

“I have never done anything like this before in my life. It’s very hard, it takes its toll but it will be worth it in the end.

“She means a lot to me and the MS Society is doing extremely good work so anything I can do for them I will.”

Mr Clark has already raised £1,300 of his £1,500 target through his Just Giving page, as well as getting friends and family to sign sponsorship forms and asking his parents in Spain to help with the fundraising.

To sponsor him, go to www.justgiving.com/fundraising/martin-clark66.