Police were forced to use CS gas to restrain the man when they entered the Zizzi restaurant in The Strand on Sunday evening.

A Metropolitan Police spokeswoman said the man was aged between 30 and 40 and that his injuries were self-inflicted.

The man was then taken to hospital in south London where his condition is stable. It is understood surgeons were unable to reattach his penis.

A spokeswoman for Zizzi said the man was not thought to have any connection with the restaurant.

She said: "At around 9pm on Sunday, a man walked into the Zizzi restaurant on The Strand, down the stairs to the basement restaurant area and tried to enter a kitchen.

"Members of staff stopped him, at which he ran into a second kitchen area.

"The man then picked up a kitchen knife and slashed himself across the wrist and groin areas before running back into the restaurant, where he continued to stab himself.

"This happened in a matter of seconds and was obviously extremely frightening and distressing for the many customers and staff in the restaurant at the time."

She added: "Apart from the man, we understand that no-one else suffered any physical injuries."