The actor had to undergo a makeover for his part in the period drama and his children were so horrified that they asked him not to meet them in front of their friends, reports The People.
"My kids banned me from collecting them from school unless I was wearing a hat and hid," said Law. He also said his eldest son, Rafferty, 15, has been teaching him street slang in a bid to make him cool.
"My oldest, Rafferty, who's almost 16, has been teaching me some London street slang because he wants me to be a bit cooler. At the moment he thinks I'm really uncool... It's utterly bizarre. It's like a new language. I sound b**ody ridiculous saying it so I've decided to stop," he added.