This video shows the dramatic moment a soldier from the Queen's Guard turned his rifle on a tourist who grabbed him outside Windsor Castle.
Friends are heard giggling as the Asian man marches alongside the serviceman - who is thought to be from the Scots Guards regiment - and rests his hand on the soldier's shoulder.
But the grin is soon wiped off the tourist's face as the soldier suddenly points his weapon directly at the man, barking: 'Get back from the Queen's Guard!'
The terrified tourist jumps back and is then seen running away, quickly learning his lesson.
The video, entitled 'Why you don't harass the Queen's Guard', was posted online earlier this week and has been viewed more than 15,000 times.
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