Quoted from Snopes.com:

The Mirror's report on this photo (headlined "My Privates Can't Control Themselves") was somewhat more tongue-in-cheek, maintaining that Colonel West did indeed pose sans underpants (but didn't deliberately expose himself):

Simon West, 39, was "embarrassed beyond comprehension" and denied that the cheeky grin on his face proved he knew exactly what he was doing.

One of his soldiers said: "We all think it's hilarious. The newspapers are selling like hot cakes."

One thing was brought out into the open yesterday — the colonel definitely had not got anything on under his kilt.

Army spokesman Lieutenant Colonel Ed Brown confirmed that Lt Col West was not wearing underpants.

He added: "The accusation he did this on purpose is utterly ridiculous."

As for the jaunty grin, apparently that is how he always smiles.

A colleague at the base said: "When he saw the picture he went bright red. He was covered in confusion. It was an extremely formal occasion.

"I am sure he'll see the funny side one day but at the moment he's not laughing. He's the boss and he knows everyone will be having a jolly good laugh."
The Mirror was, however, unable to clear up the age-old mystery of just what one might expect to find under a kilt:

His father William West, a retired major in the Gordon Highlanders, said: "We are bound by the Official Secrets Act so we can't say what's under the kilt. But my son nearly let the cat out of the bag. Luckily there was a shadow there. It's all terribly embarrassing. My daughter-in-law phoned. She said he was rather out of sorts."