British actor Robert Pattinson has fallen foul of Australia's compulsory helmet laws after police discovered a picture of him riding a bike without one.

According to the website Entertainment Wise, police in South Australia confirmed that the 26-year-old had been let off with a caution.

"He will not be fined, it is just a simple caution. We had a chat with him and told him that it is a requirement to wear a helmet while cycling a pushbike. It’s no biggie," said a police spokesman.

Police were alerted to Pattinson's bare-headed riding after a fan snapped a photo of him which was then published in a local paper.

"Someone took a picture of him when he was out cycling so that is how we knew,” said the spokesman. “If he does it again, he will be fined."

Pattinson could have been fined A$90 for riding without a helmet, plus a victims of crime surcharge of A$60, for a total of around £100.

Given the vampire-playing Twilight star has a net worth estimated at US$64 million, we're guessing that he'd just have sucked any fine up.