A 100-mile run along the Thames Path awaits two men aiming to raise funds for Project Rainbow.
They hope to collect £5,000 in sponsorship to go towards the project to construct a building in the churchyard for children's work and community activities.
Sports fan Bob, 68, is a former PE teacher and an experienced runner.
"Both Andy and I have done marathons but we've never done the equivalent of three back-to-back so that's the challenge for us," he said.
"It'll be hard work but I shall enjoy it."
The Stratford Gardens resident has completed no less than 24 marathons in all, including London nine times.
Financial controller Andy, 49, from Woodlands Park, ran the London Marathon last year as well as in 1997 and 1999.
The father-of-three is a governor at White Waltham Primary School and the treasurer at the church.
The pair will set out on Thursday, September 13 and will run, jog or walk along the riverside path through Gloucestershire and Oxfordshire.
Seeing them off on their first day will be the Bishop of Swindon the Right Reverend Dr Lee Rayfield, a former vicar of St Peter's Church in Furze Platt.
On day two they will travel towards Reading, waved off by the Bishop of Oxford the Right Reverend John Pritchard.
Both are patrons of the project.
They will return to Maidenhead on Saturday, September 15.
Other members of the church congregation will be taking part in their own three-mile sponsored event on the Saturday afternoon.
Just under £500,000 is needed for Project Rainbow. Nearly £400,000 has been raised so far.
Last year the Reverend David Andrew from St Mary's and his family raised £14,000 through a sponsored bike ride.
Visit www.charitygiving.co.uk/projectrainbow100run to sponsor Bob and Andy.
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