James Purefoy has revealed that co-star Dervla Kirwan laid down the law while filming new ITV drama Injustice.

The heartthrob plays criminal barrister William Travers in the show, which kicks off on Monday, with Irish actress Dervla playing his publisher wife.

"She's no nonsense, you don't mess with Dervla," James joked.

"If you haven't learnt your lines, if you weren't prepared, if you were trying to do something which was ego driven rather than scene driven, she would be on you like a ton of bricks!"

But despite being kept on his toes on set, Camelot star James said the cast and crew found time to enjoy themselves with themed dress-up days organised by director Colm McCarthy.

"We had Halloween day and a Wild West day because it's one of the things that Colm does and it's lovely," James said.

"But people were still very respectful of the work - you can be respectful and still wear a cowboy hat..."

:: Injustice begins on Monday, June 6 on ITV1.