Ian 'Beefy' Botham's Great British Walk - Against Childhood Leukaemia is a 52-mile (83km) trek through nine towns across the UK.
Sir Ian started his trek on Friday in Taunton, Somerset, where he was joined by hundreds of fans who wanted to help his fundraising efforts.
The walk will finish in Durham on Saturday, 18 October.
Sir Ian said his walks tended up be "a bit lonely", but this expedition would mean seeing more people as he went through towns and cities.
He said: "We found it a bit difficult in the wilds along the A9 collecting from the sheep so this time we can collect money along the route."
Starting from Somerset County Cricket Club, people can join him on a four-mile walk following the banks of the River Tone and along Bridgwater and Taunton Canal.
Some 800 pupils from Queen's College in the town were given an hour off lessons to line the route.
"When we heard Sir Ian would be walking past the school, it seemed a fantastic opportunity to raise funds for a marvellous cause and let the children meet a sportsman who's become a living legend," said headmaster Chris Alcock.
Sir Ian, president of Leukaemia Research, first met youngsters with leukaemia in Taunton 25 years ago, inspiring him to start his fundraising walks.
He said: "In 1985, when I first started walking to raise funds for Leukaemia Research, the survival rate for children with leukaemia was 20%, now the survival rate is 80%.
His techniques for getting through the challenge of walking more than 15 miles a day include not washing his feet for the whole walk.
"At the end of each day's walking, I get into the bath, my feet don't go into the bath," he said.
"You don't want to soften the skin, my feet stay out of the bath.
"My feet don't get washed for the whole walk. But they get cleaned with surgical spirit, so they're probably the cleanest bit of me."
Following Taunton, Sir Ian will take in Windsor, Tunbridge Wells, Bury St Edmunds, Stratford-Upon-Avon, Llandudno, Harrogate and Milngavie near Glasgow.
The 2008 Walk finishes in Durham, where he ended his professional cricket career.
This is the first time a limited number of people can walk with the man known as "Beefy" in exchange for sponsorship.
Copyright Speakers Corner 2016