The three boys, believed to be between the ages of eight and 11, got on the train at Blackburn, and refused to put their feet down when asked by the man, according to one witness.

“The children had their feet on the seats at first. There were three boys, aged 8-11,” explained the 17-year-old student, who did not want to be named.

“The guy went over and asked them to take them down and they were being quite cocky. The guy, who was in his 70s, then threatened them with a 'clip around the ear'. He then sat back down.

“The children then put their feet back up and wouldn't take them down. The guy then went over and tried taking their feet down. Then all I saw was the man punched one of the children in the ribs and had hold of the child’s arm in the photo.