Liz Hoggard: The joys of making a West End debut

There's something humbling about the ensemble in an age of celebrity

Do you know what a supernumerary is? No, neither did I – until I made my West End debut in An Inspector Calls, at London's Novello Theatre last week. Supernumerary is the theatrical term for "extra". A performer who appears on stage but doesn't speak. It derives from the Latin super- + numerus: ie exceeding what is necessary, required, or desired.

Frankly, as a non-thesp, it was terrifying enough taking to the stage 25 years after I last appeared in the sixth-form play. A silent role was just fine by me. But actually the supernumeraries in Stephen Daldry's adaption of the JB Priestley classic are important. They appear as a silent chorus towards the end of the play, judging the dysfunctional Edwardian family (who have caused the death of a poor working girl), from the perspective of 1945.

When offered the chance to be an extra, I thought it would be a great chance to see what goes on backstage. Thanks to Alan Ayckbourn's Noises Off, I was expecting drunkenness and affairs. I'm sad to report, it's highly professional. For a start, you can't negotiate Ian MacNeil's brilliant expressionist set (a doll's house on stilts) without absolute focus. Everything is meticulously conceived, even though you're a bit player. Wardrobe found me a 1940s costume (wool dress, heavy coat, hat), curled my hair and slapped on cake-like rouge. I tried not to notice that I'd morphed into the middle-aged woman I spend my life trying to avoid.

"What's my motivation?" I asked eagerly. Jonathan the stage manager smiled tolerantly: "It's a bit more generic than that." In fact the supernumenaries are Daldry's invention. Adapting the play back in 1989, he found the Detective (the play's "socialist" deus ex-machina) uses the pronoun "we" a lot in the original manuscript. So he created a Greek-style chorus. Supers (as they call themselves) can be amateurs with a passion for the stage. Or creatives topping up their salary. The lovely women who guided me were drama teachers, opera singers, even a pop star who performs with Chas Jankel of The Blockheads.

Thanks to them I didn't make a complete fool of myself. Though I was nearly decapitated (that bloody hat!) scrambling into the house at the end before it explodes. I was astonished how relevant the play still is – with its message of social change (1945 voters of course ushered in the Welfare State).

The funny thing is Priestley and I have history. Aged 17, I was in the school production of When We Were Married, playing an aged crone. In public for the first time sans National Health glasses, and with a flattering amount of foundation, I thought: "Maybe it's going to be all right." Then they applied the wrinkles. I was so upset I rubbed them off. Furious, the director accused me of not being a team player. He was quite right. I've never acted since. But, looking round the Novello's marble and gilt interior, I finally got it. In an age of celebrity, there's something humbling about the ensemble.

The individual is stronger as part of a team, whatever David Cameron's new Tories might suggest. In the word's of Priestley's Detective: "We don't live alone. We are members of one society. We're responsible for each other."