London, Sept.29 : A rude gesture by one of Queen Elizabeth II's guards last night left visiting tourists outside Buckingham Palace shocked, and him in trouble.

According to The Sun, the guard's hand signal was videoed by an American sightseer and posted on the website YouTube.

The sentry is seen moving his clenched fist up and down, apparently in a joke insult to a comrade.

Palace guards are strictly forbidden from communicating with anybody while on duty.

Household Division sources said the guard can expect to receive a major rollicking from his commanding officer, a heavy fine and extra duties.

He is believed to be from the Nijmegen Company, a ceremonial unit of the 1st Battalion of the Grenadier Guards.

A Foot Guards officer said the guard has not only violated the rules that go with his job, but also embarrassed the Queen and "made the regiment look like thugs."

Top brass at first suggested the gesture was a military signal for "Hurry up".

But the video leaves no doubt about what the soldier means.

An Army spokesman said last night: "We're identifying the individual. This behaviour is unacceptable." (With inputs from ANI)