A pair of military gym instructors more used to handing out gruelling physical tasks than doing them are to put themselves through a 24-hour workout for charity.

RAF Corporals Chris Gore and Shane Phipps, both 28, have lined up a gruelling physical task on the hour every hour during a 24 hour CrossFit session.

Cpl Gore, who is originally from Liverpool, said he hopes to raise at least £500 for Great Ormond Street Hospital and the Royal British Legion after his cousin recently lost a young child.

He added: "It is going to be horrendous, around 3am is going to be quite cheeky because there’s not going to be many people around to gee us up.

"Word spread around the whole base that we were doing this challenge and a lot of people are saying they will come down and see us.

"The whole thing with me being the person that usually issues the workouts has given this an extra edge."

Despite the challenge not taking place until November 6, word has rapidly spread across Northwood headquarters and dozens of service men and women are expected to cheer them on through the challenge on November 6.

The two challengers will also be accompanied throughout by a DJ who is going to complete a 24 hour DJ set at the same time.

To sponsor Chris please visit http://www.justgiving.com/24hourCrossFit