It’s kind of calling-for-immediate-attention bell that invites a sharp smack with palm or finger, and drives Basil Fawlty to the very verge of derangement. Ping! It’s a comedy device – an indicator of short-fuse entitlement, an enhancer of retro-farce chaos. It retains its comic tinge in Amsterdam, which is unnerving, given the context. – David Jays