Celebrity chef Nigella Lawson was banned from flying to the US because she confessed to taking illegal drugs, according to a report.
The 54-year-old, who is a judge on cookery show The Taste in the US, admitted she had taken cocaine seven times and also to smoking cannabis during a court hearing.
Ms Lawson went to Heathrow on Sunday morning to catch a British Airway flight to Los Angeles. The Daily Mail reported that she was thought to have checked-in and cleared security when she was told she would not be allowed on the flight.
"She didn't seem to say much, but she did not look happy. She could not get on the flight so she had to turn around and leave," a witness told the paper.
The US asks people if they have ever been arrested or convicted in relation to illegal drugs. It can decide to prevent entry to the country even if the person involved was never charged.
The US Department of Homeland Security said it did not comment on individual cases.
But a spokesman said foreign citizens who had admitting committing drugs offences could be deemed "inadmissible".
"In general, an alien found inadmissible will need a waiver of inadmissibility," he said. "Depending on the basis of their refusal they may be eligible to apply in advance of travel for a temporary waiver of inadmissibility. The waiver application process can be lengthy."
A spokesman for Miss Lawson said: "We would never comment on Nigella's travel plans."