Downing Street has rejected suggestions that David Cameron might have caused a security breach by briefly leaving his official ministerial red box unaccompanied on the table of a train carriage.

A train passenger took a photograph of the red box, which was published by the Daily Mirror. The passenger told the paper: "It was just sitting there. I could probably have run off with it if I'd wanted to."

The transport minister Simon Burns caused controversy earlier this year over his use of an £80,000-a-year chauffeur-driven government car to commute daily between his Essex home and Westminster, claiming he used it only because he was barred from working on his red box of official ministerial papers on the train for security reasons.

The Cabinet Office contradicted this, saying ministers could work on papers in public as long as they ensured sensitive material could not be seen.

He is lucky that the public are more honest than MP's. If Cameron is incapable of looking after a red box he should be made to stay in the office until it is finished than be allowed to travel with it.

He left one of his kids behind in a pub FFS. It's hardly a surprise he might tottle off without his red box.

He always has a few police with him (in plain clothes) so im sure there was no danger

I am surprised that one of those officers did not mention it or stay with it.