The group, serving with 1st Battalion The Royal Irish Regiment, took on the challenge at Forward Operating Base Shawqat, in the Nad-e Ali area of Helmand province on Christmas Eve.

They included Major Eamonn Coogan, 49, from Beaconsfield, who decided to take part at the last minute after his colleagues told him he was "past it".

Major Coogan, who has 32 years' service and 18 operational tours under his belt, set off on the 26.2-mile marathon at 4am, two hours ahead of his colleagues. He said: "I had been asked some months ago, when it was first being planned, whether I would like to take part in the marathon and I had declined, saying that at my age it probably wasn't a good idea. But the day before the marathon I heard two officers discussing it and one of them said 'Eamonn used to be a fantastic runner but he's past it these days'.

"I popped out from behind my desk and told them I was past nothing. I was going to leave it at that but I went to bed that night and couldn't get the idea out of my head that people thought I wasn't the person I used to be. So I decided that I would show them."

The father-of-four, originally from Birmingham, who finished in five hours 21 minutes, added: "I am in my 32nd year of service with the Army and I very much enjoy the physical requirements of soldiering. Unfortunately I will retire next year but I do keep myself fit and I think I proved to me colleagues that I'm not past it yet. I felt a bit stiff afterwards but much better for doing it."

Lieutenant Claire Westerman, 24, from Southampton, Captain Jon Toomey, 33, from Warminster, and Captain Gregg Hutchison, 32, from Armagh, ran the marathon in preparation for a 350-mile endurance exercise they will take part in next year. The Exercise Boru's Bound in April will see them run from Tern Hill, Shropshire, to Stranraer in Scotland before boarding a ferry to Belfast where they will take part in the city's marathon in a bid to raise more than £20,000 for the Army Benevolent Fund, the Royal Irish Benevolent Fund and Help for Heroes.

Lt Westerman, a unit education officer, said: "It was hard work of course, but it was great training for Exercise Boru's Bound, which will be the real challenge. Forward Operating Base Shawqat is not the biggest of bases, so 96 laps got a bit repetitive and brain-draining - but there was plenty of banter and we had a good laugh."

Captain Toomey said: "This was my first ever marathon so it was quite daunting - although I suppose the really daunting thing is the 350 mile Boru's Bound coming up in April. As it was my first attempt though, I was happy to complete it within four hours and felt really good about it afterwards. I'm sure my feet will stop hurting soon."

And Captain Hutchison said: "It was a cold start at 6am and I still hadn't really warmed up by the time I finished it four hours later. Everyone put in a strong performance and it was an interesting way to spend Christmas Eve."