1 Don’t just switch off your mobile in response to what’s very likely a cute invitation from some fake-friendly voice. Make sure it’s off before you enter the theatre, thus making sure that you’re not publicly humiliated by Richard Griffiths or A.N. Other.

2 Never whisper, let alone talk, during the performance. If you’re hard of hearing, hire a loop rather than bother your companion for info about the plot. And don’t hum along with songs, even if they’re by Rodgers and Hammerstein.

3 Don’t bring picnics. In fact, don’t eat anything, not even your fingernails, even if the play is, well, nail-biting. If you must buy an ice cream in the interval, make sure you finish it and dispose of the carton before the restart. The scraping at remnants sounds like scratching on a wall.

4 If you fear that you’ll cough, bring a handkerchief to smother your mouth and pastilles to put in it. Considerate theatregoers would rather asphyxiate than interrupt a good actor.

5 Always apologise if someone is forced to stand as you make your way to your seat, but if you are late (and you should never be) reduce your apology to a quick, sorrowful nod.

6 Don’t clap actors’s entrances, even if they’re famous, or their exits, even if they make them in the swaggering style that half-invites applause. All this is dated and naff and makes you look like a celeb-hungry prat.

7 Have nothing to do with standing ovations unless a performance is close to a once-in-a-lifetime experience. In America such ovations have become meaningless and, if they don’t occur, they indicate disapproval. We don’t want them to become regular here.

8 If a friend is on stage in a comedy or farce, or has written one, don’t pile on the laughter. The artificiality is usually transparent enough to make failure more and not less likely.

9 If you must go to that often obnoxious, spuriously glitzy occasion, the first night, don’t ponce about pretending to be an important guest, even if you are one. Think of your fellow audience members and the actors, both of whom want to get on with the show. And that show isn’t about you.

10 No need to dress up, let alone wear dinner jackets and evening gowns, as was once the case. But try to be a little better dressed than the critics, who often look as they’ve been grabbed from a washing machine that hasn’t yet been turned on.

11 If you see a sleeping critic don’t necessarily wake him or her up, as guilt is likely to ensure that his or her review is more favourable than it might otherwise be. But don’t let him sleep too deeply or he may (and this has happened) crash into or across an aisle, causing injury to the innocent. And snoring is unacceptable, whoever does it and however awful the show.

12 If critics irk you by scratching notes on a pad, be forgiving. They’re only doing their jobs. And virtually all critics accept that lighted pens, once common, are now verboten. If you see a critic turn one on, whisper something tactfully germane, like “you blind sod, switch it off”.

13 If the child you’re bringing is chatty, gag it. If it’s fidgety, handcuff and shackle it. And if you’re altruistic enough to bring a school party to a Shakespeare matinée, threaten potential wrongdoers with tickets to the next revival of Timon of Athens, to be followed by a ten-page essay on the ethics of Apemantus.

14 Try your hardest not to be tall, which means shunning headgear and primped-up hair. And if you can’t help your height, ask for a seat on the aisle or somewhere where you won’t interfere with people’s sightlines.

15 If you are maddened by a fellow member of the audience, postpone a serious or violent encounter until a suitable pause in the action, preferably the interval. But usually a schoolmarmy stare and an English sniff, followed by a reproachful smile, will suffice.

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