Wales rugby great JPR Williams received a 17-month ban for drink-driving on Monday after a court heard how the legendary full-back tried to deceive a breath test by placing coins in his mouth.

Williams, a key member of the successful Wales teams of the 1970s, was also fined STG380 ($A630) after admitting the charge.

Cardiff Magistrates' Court was told how the 61-year-old was stopped in his red Audi car after spending the day watching a match.

Hannah Norton, prosecuting, said officers immediately smelled alcohol and took Williams, who worked as a surgeon, to a police station.

"Mr Williams had to be instructed twice to remove items from his mouth, those being three penny coins," she said.

"Your worships, there is a myth that copper from those coins can interfere with breathalyser machines at the police station."

A blood sample showed he had 142mg of alcohol in 100ml of blood. The legal limit is 80mg.

The court heard how Williams was chauffeur-driven to London to watch London Welsh, one of his old clubs, with another former international player on January 30.

He was taken back to Cardiff where he left his car and was stopped by police in the Welsh capital while driving home to Llansannor, near Cowbridge, in the Vale of Glamorgan.

Williams, who starred for the British and Irish Lions teams that triumphed in New Zealand and South Africa in 1971 and 1974 respectively, was told to put his handbrake on when he was pulled over because he appeared not to realise his car was rolling backwards, the court heard.

Nigel Daniel, Williams's lawyer, said: "In what he now accepts was a very stupid and misconceived decision, he got in his car and headed home back to the Vale of Glamorgan.

"Dr Williams was under the foolish misconception that after a four-hour journey he was now fit to drive."

Williams was "extremely remorseful", he said, adding: "He feels he has let his family down, his friends and of course those who hold him in high regard for his sporting prowess."

Williams's ban will be reduced by four months if he carries out a driver rehabilitation course.

Speaking outside court, Daniel said his client hoped his case would serve as a warning to other motorists.

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