John, 54, will spend May 24 and 25 walking 100 miles in the Yoredale 100 challenge, an event organised by the Long Distance Walking Association.

It's the walk of his dreams, both in terms of walking country - his beloved Yorkshire Dales - and the mental and physical challenge, but for John the most important factor is that it will raise money for Cancer Research UK.

John, of Eastwood, has revisited the site of his first walking challenge for Cancer Research UK as part of his training for the big event. He was inspired to walk the 50 mile Mary Towneley Loop to mark his 50th birthday after losing close friends to the disease and trod it again at May bank holiday.

Cancer Research UK is the largest single funder of research into the disease in the world and needs the money to continue making advances in basic research, clinical research and drug development, population research and information provision.

John said: "I hope as many people as possible will support my challenge because every bit of money raised for the charity is important. The next £100 we make could be the money that turns the key to unlock some area of research into the disease," he said.

"Thinking about that keeps me going towards the target. Cancer is something that effects everyone in some way and every bit of research is vital."

The 100-mile target is like doing four Todmorden Boundary Walks in two days but despite a bad chest infection knocking 16 days' preparation off, John is happy with progress going into the last days before the walk.

Completing the Mary Towneley Loop walk in 17 hours was the distance walk he wanted to get under his belt and having put those miles into the legs a series of shorter (by distance standards) but faster walks have also gone well, as he reports in his online blog.

He has also scouted out more of the actual route and is also working on the right mental preparation for what is an enormous task.

"It is a big challenge and I'll split it down into distances - 25 miles is a fifth of the distance, by 52 miles, where the Hawes breakfast stop is, we're just over half way. Buckden is two thirds and then you can start thinking about diminishing the distance from checkpoint to checkpoint.

"I'm quite excited now, and looking forward to it. All my training has been near home so it was great to get up there last Sunday and see walking country that looks fantastic," he said.

John has a website, www.shack-100.co.uk, which outlines aspects of the challenge and provides an online link where people can sponsor him.

In addition to more traditional methods of collecting sponsorship, John hopes it will reach people outside of the Todmorden and Hebden Bridge areas too and bring in even more money for the charity to research and fight the condition.

Meanwhile, cheques payable to Cancer Research UK can be sent to John at Rose Cottage, Higher Eastwood, Todmorden, Lancashire, OL14 8RU.