I thought if he wants to thump the cashier again he'll have to thump me first

Nicholas Owen

According to Mr Owen the attack happened after an argument between a woman and the cashier.

"Inside her car were three younger people who I took it were her children.

"Then a young man jumped out, he kicked his way through the locked door and dashed across to the cashier and started giving him a severe beating with his fists," he said.

Mr Owen, who boxed at school and still does boxing training, decided to try to help the cashier.

"I went in and shouted at the top of my voice," he said.

Dodgy situation

"The cashier was on the floor by this stage, I shouted 'get off, get off' and I think the guy was so shocked that he did."

He persuaded the assailant to move to the other end of the shop but the teenager was still intent on attacking the cashier.

"I thought if he wants to thump the cashier again he'll have to thump me first," said Mr Owen.

Police were quickly on the scene and arrested a 17-year-old youth on suspicion of assault and criminal damage.

Mr Owen, whose son Anthony, 25, is training to be a Metropolitan Police officer, said: "You either wait for the police or you do something.

"It crossed my mind that it could be dodgy but I just felt I had to do something.

"I'm just glad I'd been to the gym recently."