Now look. The whole point of having multiple checkout operators in supermarkets is so that multiple queues of people can be served in 'parallel', i.e. all at once. If there's a problem with one queue, it shouldn't affect the others, otherwise the whole system breaks down. Which is why supermarket huddles are so frustrating. Mavis: "Alice! This customer has some vouchers (or whatever) I don't recognise!". Alice leans over, abandoning her own customers: "Hmm... I haven't see that before, either. Gladys?" Gladys peers over from aisle 3's checkout: "Yes, you just have to press D and then 56.... oh, hang on, I'll show you." We now have three people sorting out the one problem and noone's getting served. I've seen this syndrome in banks, post offices and many other establishments where there are more than one operator. And it drives me mad. Look, if there's a problem, call in a manager, or the cleaner, or 'phone a friend'. But HANDS OFF the other queues!