Nigella Lawson banned from entering US.

Nigella Lawson has been turned back at London's Heathrow Airport after being banned from the US for admitting to using cocaine.

The celebrity cook was due to fly to Los Angeles to act as a judge on TV cooking show The Taste, but was not allowed on the plane.

Lawson admitted to prior cocaine use under oath during a trial last month, but Scotland Yard decided not to act on her confession.

But US authorities have taken a tougher stance, the Daily Mail reports, banning her from entering the United States. She left her bags at first class check-in but was turned back at the security gates, a witness said. "She didn’t seem to say much, but she did not look happy," the unnamed onlooker said.

"She could not get on the flight so she had to turn around and leave."

The US reserves the right to ban visitors to their country if they have admitted to drug use, even if they have not been convicted.