Former England cricketer Lord Ian Botham says he is "proud" of his fundraising walks for leukaemia research, describing them as "a lot of fun and pain".
The former Somerset player raised more than £12m for charity, with his first walk taking place in 1985.
Lord Botham said the challenges started after he saw four children at Musgrove Park Hospital in Taunton when he was receiving treatment for a broken foot.
"The doctor said well you've got eight to ten weeks for treatment and I don't think those boys will be with us and, at the end of my treatment, they weren't. I said to Kath, we have to do something positive."
He added: "It's all about awareness. The leukaemia walks was the awareness and in those days there was a 20% chance of survival, now it's a 94 to 95% chance. So that is terrific."
The money raised by Lord Botham over the last four decades has supported Blood Cancer UK (formerly Leukaemia Research).
He talked about the impact of his walks while discussing his new book, Seasons: Riding the Torpedo, during an interview with BBC Breakfast.
"We did 18 walks, ten and a half thousand miles, that is the equivalent from London to Sydney.
"It started off we didn't know what we were going to achieve, we didn't know it was going to work out, but the response from the public was immense."
The last challenge took place in 1999.
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The all-rounder, who represented England from 1976 to 1992, said a lot of "sacrifices" were made to make the walks and his cricket career possible.
"It was a family affair," he continued.
"The toughest job of the lot and that's the organisation. These walks took about 18 months to organise with my wife and children."
"I get a lot of stick from the grandchildren, they said to me, you were the worst father because I was never there. I was all over the world playing cricket.
"When the grandchildren came along, I got a big mug one morning saying best ever granddad. So it balanced out, but yeah, you do make a lot of sacrifices. That's where the family comes together."
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