Turning your back on a troop of soldiers is never a good idea.
And this hapless man, with a camera slung over his shoulder, found out the hard way when he stopped to chat to a woman as the Queen's Guard marched by.
The first soldier passes by him without incident, before the man is bumped into the fray. Only then does one of the soldiers tell him to "make way".
Story continues below
Queen's Guard march into man
A woman can be heard saying, "Guards coming down, Derek. Mind! Mind!" moments before he is caught off guard.
A bystander later calls out "stupid man".
The video, which was uploaded on Tuesday, has already got over one million hits.
Steven Macaulay, who shot the footage, captioned it: "You better be on your guard when the Queens Guards are coming through, these guys aren't stopping for anything!"