Bobbies on the Beat
British policemen and policewomen walk a beat, that is a specific path, around their neighbourhood. Along the way they stop to ruffle the hair of small children, have cups of tea, help little old ladies across roads and say ''Ello, 'Ello, 'Ello what's going on 'ere then?' in Northern or cockney accents.
They carry truncheons instead of guns and American film makers seem to think that for a scene set in England to be authentic they need only put a Bobby in it, no matter how utterly improbable (Bobbies on planes etc.). See also Double Decker Routemaster Buses and Red Telephone Boxes.
Bobbies are sometimes called other names but we can't think of any of them just at the moment.