The 40-year-old, former Hebden Bridge runner will take on the Paris Marathon on April 6 and then run the 250 miles to London for that city’s marathon on April 13.

He will be raising funds for Children with Leukaemia.

Iain’s parents, Phil and Sandra Lomas, of Mytholmroyd, are hoping Calderdale folk will sponsor him on behalf of the West Yorkshire Forget-me-Not Trust, which is building a children’s hospice for families in Calderdale and Kirklees.

Iain, a former Royal Marine, was part of a four-man Dartmouth crew which rowed the Atlantic from La Gomera to Barbados in 2004 in just over 36 days.

And in October 2007 he ran the Kalahari Desert in South Africa, which involved running six marathons in seven days in temperatures reaching 50 degrees.

He is hoping his current high fitness levels will stand him in good stead for the next challenge.

“I did a lot of training for the Kalahari and am training as much as I can, but a lot of it is is the mental challenge and trying to prevent injuries,” said Iain, of Dartmouth, who will be running with two friends.

“Mum is hoping to raise funds for the Forget-me-Not Trust and if people will support that it will be fantastic.”

Iain attended Calder High School, Mytholmroyd, and was a trombone player with the Hebden Bridge Junior Band.

In 1984 he joined the Royal Marine Band Service and is currently a builder in Devon where he lives with his partner, Amanda and their 16-month-old-son Ben.

“We are very proud of him but think he is crackers,” said Mrs Lomas.

Iain also has three sisters, Allison, a deputy head teacher in London, Sarah, a senior cardiology nurse in Harrogate, and Mandy, of Houston, US, who is married to the astronaut Piers Sellers.

Anyone wanting to give money to the trust should call 01422 884153.