Green Park station, Victoria Line Northbound platform, one day last week about half past four.
Over the tannoy: "Will all station cleaners please report to the station supervisor's office IMMEDIATELY."
One minute later: "Will all station cleaners, who are sitting in their mess room drinking tea and watching telly, report to the supervisor's office IMMEDIATELY."
Ten seconds later: "Will the cleaner who is walking past the mess room please open the door and tell all cleaners inside to put down their tea and report to the supervisor's office IMMEDIATELY. Thank you."
One of the few occasions when passengers actually look at each other. And smile.