The Newsroom star drove off without looking around her unlocked vehicle and was puzzled about the strong smell of beer. She stopped at a red light and turned around and found the vagrant had made his way into the car while she was at a party and was now snoozing.

The Shutter Island actress says, "It was quite late at night... and I went into one of those underground car parks and I had an old 1960s Saab that I never bothered locking, because it was falling to bits and no one wanted to steal it.

"I got in and there was a most terrible smell; I guess it was pee and beer or something... I kept thinking it must be the car park, but when I got out of the car park it was still there... I stopped at a red light... and I turned around and there was a man fast asleep on my back seat.

"There was about five horrible minutes where I was driving around London with this man asleep on my back seat and I kept looking at him in the rear view mirror and thinking, 'I don't know what to do. How is this gonna end?'

"Eventually he woke up and he just sat up and I screamed and he screamed, and I stopped the car... I think he just opened the door and out he got."