Two Army officers based at Colchester Garrison are running a marathon for charity - and each other’s jobs.

Lieutenant Colonel Mike Shervington, commander of 3 Para, and Captain Felix Wright, commander of the battalion’s 6 (Guards) Platoon, will race the Halstead Marathon on Sunday.

The pair are raising money in support of the 27th Colchester Brownies, who are predominantly made up of members of Army families, and Leukaemia & Lymphoma Research in support of one soldier’s daughter, herself a Brownie, who is being treated for leukaemia.

But to add a competitive edge to the race the fastest of the pair will get to take on the other’s job for a day in a bet hatched up six months ago between the two soldiers.

It means Capt Wright has the chance to take control of the whole battalion for a day - up from 28 men to 650 - and boss around his senior officer, though he also risks losing his command and being relegated to the ranks for the day.

Lt Col Shervington, 42, said: “We took on this bet over a bottle of wine and by pure laws of physics there’s no way he should lose.

“He has done a half marathon in one hour 25 minutes, which I have never done, and if he doesn’t win it’s criminal and quite embarassing for him. I’m also a relatively old man.

“But I am determined not to allow him to win and all I can rely on is the hare and the tortoise scenario.”

He jokingly added: “His men said they are looking forward to me taking over as they feel stifled under his leadership.”

Capt Wright, 29, said: “Although Lt Col Shervington is trying to play the underdog card I think he will be pretty strong and it will be very close. I’m not sure age is on my side, I’m not sure being younger is an advantage.

“I’m hoping it does not come down to a sprint finish.

“If I win the bet I have a few things lined up but I’m keeping it all close to my chest. Either way it will be good fun.

“Not my soldiers’ lives, but a day in their lives, are in my hands, and they will not let it slide if I lose.”

Capt Wright hopes to complete the route in three hours, but recognised it is a hilly course, while Lt Col Shervington’s previous best time was three hours 15 minutes.

Each year the 27th Colchester Brownie pack take on the Leukaemia Challenge, doing 26 different things to raise money for both the charity and group activities.

Colour Sergeant Chris Prosser, whose daughter Chloe, seven, is being treated for leukaemia, said: “For me this event means a lot because the battalion have supported me and my family through-out the entire process.

“There are very few organisations which give the support that we had with cars, organising accommodation close to Great Ormond Street Hospital, the time off and the support back here for on-going treatment.”

Chloe is still being treated for avascular necrosis, a condition caused by radiotherapy which affects bones, and may longer-term need a shoulder and hip replacement.

Colour Sgt Prosser, 36, added: “Chloe knows a lot of my peer group and feels part of the battalion - she can come onto camp and everyone talks to her. She has grown up in an adult environment and this support means a lot to her.”

To sponsor the pair visit www.justgiving.com/felixjwright.