"I started my long career at JS as a trolley boy at Lewisham. We had an odd system of dealing with customers taking trolleys from the branch. When a customer knew they wanted to take the trolley out, they told the cashier who left a gap on the customer receipt and then charged them £1 to take the trolley out. Someone was always stationed by the exit, checking that everyone with a trolley had paid their pound (or paying at the cigarette kiosk if not) and kept their receipt. When customers returned with their empty trolley, the trolley boy's job was to tear off the bottom part of the receipt, and then insert a token (about the size of a modern 10p, but with a hole in the middle) into a machine on the wall. The machine then slowly dispensed two 50p pieces, which we collected and passed back to the customer. This system remained in place until I left the store just before scanning checkouts arrived, so I'd be very interested to see what they did when GMS scanning came in!