I reckon they didnt care.. and that at least being parked right outside the store - they knew the cars were safe... I mean.. would you really want to park your £1.2 million car in a pay and display car park???
I think not!
They knew they would get clamped... and its loads of free publicity too!
If I were them I would do the same... (well as long as they wouldnt get towed away!)