Ian Brennan is tackling the endurance race dressed as Scooby Doo.
Mr Brennan, 43, of Churchward Close, Grove, aims to raise £1,250 to buy new play equipment for Millbrook Primary School.
Talking before the race, he said: “I think we will have a really great first six to seven miles.
"The worse bit will be from 13 to 20 miles when you realise you have to do the same distance again.
“I hope it will remain cool. I don’t want it to rain as the costume will get too heavy and if its too hot then I will get hot.”
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