The expressions 'U' (Upper Class) and 'Non-U' (non-Upper Class) came to prominence in Nancy Mitford's Noblesse Oblige (1956). Today, some of her proscriptions seem bizarre (spectacles, not glasses; looking glass, not mirror). Language is ever-evolving and society is visibly relaxing - a preoccupation with the minute calibrations of social class is looking increasingly outmoded.

However, if you are anxious to pass muster in more class-aware environments you should remember the basics: loo or lavatory never toilet; sofa never settee; napkin never serviette; supper never tea; drawing room or sitting room, never lounge or front room.

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