After having lunch at the steak restaurant on the left side of security (airside) of LHR T5, I was charged several transactions up to 800 pounds on my AMEX. They used names like XXX city council parking fee, and they even had a website searchable on google.

I believe there are some dodgy individuals cloning credit cards in T5's shops and restaurants and using those for fraudulent transactions.

Just remember never to let your card out of sight, and check your CC statements, and avoid using your card at any T5 shops.