Actress Samantha Morton has described how she intervened when she saw a woman being "physical" with her child.
The award-winning star said the incident happened recently on the Eurostar.
"There was an American woman and she looked incredibly wealthy," she said.
"She was physical with her. I went over and said 'Hi, I don't mean to be nosy but please don't do that to her'. She was only about five."
Ms Morton also called for a change in the law in the UK on striking children.