The Daily Mail posted the picture shown above with the caption, "Queen's Guard pulls a face for tourists – now he's in trouble with his bosses".
It is not clear if he is breaking rank or just trying to amuse some tourists on what appears to be a windy day.
Nevertheless, the video has provided a few minutes of entertainment to many across the world.
It has not been confirmed whether the clip is real or a clever prank or a viral hoax, but a Ministry of Defence spokesperson has told the Daily Mail that they were aware of the video and that the investigations are being held.
If it does turn out to be legitimate, the man, who appears to be a member of the Grenadier Guards, could be facing disciplinary action.
The spokesperson said, "We are aware of the video and will investigate its authenticity". She added that, "Should any member of personnel be found to have fallen below expected standards of behaviour, they may be subject to disciplinary action".
Clad in their distinctive red tunics and bearskin hats, the soldiers of the Queen's Guard are charged with protecting official royal residences and have a history of over 350 years, having defended monarchs since Charles II took the throne in 1660, after the English Restoration.
The strict guidelines to be followed by soldiers of the Queen's Guard while dealing with nuisances include stamping their feet and shouting and is followed by raising their rifle, which is considered the final warning. After that, the guardsmen are allowed to detain the person in question.
While it is pretty rare for guards to break their stony expression, earlier this year, an American tourist managed to raise a giggle from a soldier dressed in the uniform of the Household Cavalry Regiment while rolling out a string of jokes.
The recent viral video has received mixed reactions from viewers, with Constance Jones tweeting, "This is the FUNNIEST story of the day!", while BigGold, who prefers to believe that the Guard made the faces unknowingly commented on the YouTube video, "He was soaking wet licking the rain cause he can't wipe it. Leave this dude alone."
Watch the video below: