The Queen's Guard are known for their ability to remain stoically at attention outside England's royal residences.
But one Asian tourist visiting Windsor Castle, about 25 miles outside of London, learned the hard way of the frightening consequences if you get too close.
A video posted to YouTube shows the mischievous tourist mocking the patrolling soldier by walking alongside him, as friends can be heard giggling in the background.
But the mood changes very quickly when the man rests his hand on the soldier's shoulder.
In the dramatic 20-second clip the soldier suddenly draws his bayonet-tipped rifle and shouts at the man to get back.
"Get back from the Queen's Guard," the soldier barks.
The Queen's Guard has protocols to deal with people who are being annoying, and should shout or stomping their feet. After reviewing the incident, the Ministry of Defense has said the reaction was appropriate and no further action will be taken.