THIS is the shocking moment a thug floors a security guard with a single punch after he stopped him and his friends from entering a Sports Direct store.

The youth dropped the employee with a vicious right hand to the jaw after he took hold of his coat and tried to escort him away from the shop in Wembley, North West London, shortly before 6pm on Thursday.

Video filmed by an onlooker showed the victim fall backwards and smash his head against a door,.

The attacker then runs away before the man was able to recover.

A ten-second clip of the attack - first shared on WhatsApp - went viral on social media over the weekend with more than 1.7 million views.

It shows the security guard arguing with a youth dressed in a black hooded coat and wooly hat, as his friends gather round them in the shop doorway.

The employee tells the youth to "clear the way” then appears to take hold of his sleeve and starts dragging him away from the store.

Suddenly, the youth plants his feet and swings his fist into the man’s face, catching him off guard and knocking him to the ground.

A girl screams "oh my God" as the man cracks the back of his head against the edge of a door and the thug panics and flees.

The youths are then heard laughing hysterically in the background as the shaken employee staggers back to his feet.

Some social media users suggested the security guard got too close to the youth.

Huss Montana Hoca wrote: "As a fellow security guard myself, been in these situations before. You can tell by the youth's body language that something can happen at any given moment. Lesson learnt, next time keep your distance."

John Lashley said: "Why would you ever get within strike range and not have your guard up? Hand's tucked into (his) vest."

Allan Francis added: "What a low blow, guy wasn't even looking."

A Metropolitan Police spokesman said: "Police were called at approximately 5.50pm on Thursday, November 8, to reports of a man assaulted at a shop in Central Square, Wembley.

"The man, aged in his 30s who worked as a security guard at the venue, had stopped a group of four males from entering the shop. He was then punched by one of the males before all four fled the scene.

"The victim did not require hospital treatment. No arrests have been made, enquiries into the circumstances continue.

"Anyone with information is asked to call police in Brent on 101 and quote CAD 6195/8Nov or call Crimestoppers anonymously on 0800 555 111."

Sports Direct has been approached for comment.

So fucking disgusting.