Soldier Jason O’Callaghan is aiming to raise £1,000 for the Forever Friends Appeal by taking on the 100-mile Endura Trek Lionheart Cycle on March 17.
Mr O’Callaghan, who was recently promoted to sergeant major in the Tidworth-based 2nd Royal Welsh battalion, wants to support the charity’s campaign to fund a new cancer unit at Bath’s Royal United Hospital.
The Lionheart race, now in its third year, starts and finishes at Longleat House.
Mr O’Callaghan, 36, of Victoria Fields, Warminster, who lives with wife Kelly and children Lauren, 11, and Oliver, 8, has been in the army for 17 years and decided to enter last week.
He said: “I do a lot of cycling, but I wanted to raise some money for a good cause.
“It’s quite short notice, but I am hoping to raise at least £1,000. There are different medals, depending on how fast we finish, but I’m hoping to get the gold by doing under five hours and 45 minutes.
“I’ve started increasing my training and I did 20 miles the other day, although it was harder than I thought because of the high winds.”
To donate, visit the web page www.justgiving.com/ Jason-Ocallaghan