Staff were filmed looking on in terror as a man smashed in the door of a McDonald's in West London yesterday.
Footage shows a worker teaming up with delivery drivers to keep the exit door closed as a brawl erupts outside.
He says: "I can't lock it when it's being pulled too hard", adding: "Why are they fighting? Why are they here?"
A man is later seen kicking and flinging a large object at the already smashed glass pane of the door, while workers inside back away in fear for their safety.
The incident took place at a branch's delivery kitchen in Twickenham, Feltham around 4pm on Tuesday, said the fast food chain.
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Metropolitan Police officers were called and the members of staff involved are being supported, it added.
Towards the start of the video, a group of around eight people gather outside as a woman repeatedly yells: "Get over there."
They appear to leave with a delivery driver saying: "They're running away".
A frightened worker then warns: "Stand back from the door, you don't know what they're going to do", as two people return to the area.
One man proceeds to boot in the door, with the sound of crunching glass heard as the couriers spring backwards in surprise.
He then throws a large, square object towards the pane while one person yells: "Where is the police?"
A delivery driver holds a phone up to his ear as three girls approach the door and demand: "Get out here, come out."
The circumstances that led up to the incident have not yet been made clear.
A spokesperson for McDonald's told The Mirror: "We are aware of the incident which took place at our Hanworth delivery kitchen yesterday.
"The safety of our crew and our delivery partners is of paramount importance to us and we are supporting those involved.
"The police were called and we continue to assist them in their investigations.”
The Mirror has contacted the Met Police for comment.
