When mum is in the stalls

If you're starring in a controversial West End play, it's hard to forget who's in the audience, admits Olivia Williams

(ALASTAIR MUIR)

We are now nearing the end of the run of In a Forest Dark and Deep, and it is possible to look back with affection over the experience. November 2010 seems like a lifetime ago, when I met Matthew Fox, my co-star, at a highly contrived dinner held at one of those private members clubs that has gone for the port-quaffing rather than the coke-snorting vibe.

Matthew and I were sat next to each other at one end of a long table, while producers, director-writer, agents and managers watched to see whether, in animal behavioural terms, we sociably groomed fleas from each other's fur or ended up throwing faeces in a fit of aggression. While the characters we were to play throw quite a lot of faeces (we are still in animal behavioural terms, you understand), it is important that the actors are able to mutually and affectionately de-flea, if the rehearsal process is going to be at all productive. So like a couple of shy pandas, we talked about the weather and the traffic while the zoologists took notes.

I eventually deflected this painful scrutiny by talking to Matthew's charming Venetian wife about the San Zaccaria Bellini, while furtively trying to get a real-life impression of the handsome and oh-so-familiar face of Dr Jack Shephard from Lost.

By the end of dinner, no one had been fired, so it was considered a success and as we drifted into the night, I remember Matthew confidently asserting that he would be off-book by the readthrough. I think I said something along the lines of, "Hey, TV Boy, we're not doing a page of dialogue a day on a beach in Hawaii NOW," and snorted derisively at the thought that it would be POSSIBLE to recite 82 pages of dialogue unrehearsed from cold and solitary line-learning.

Imagine my, well, frankly, my fear and shame when two months later I have spent two hours a day with my line mule, and while I have at some point known every part of the play, I have never known all of the play at any one time. We arrive at the readthrough and Matthew's script is nowhere in sight. He performs the role perfectly across the readthrough table while I bury my shame in my script and mumble along.

The game of catch-up began cordially enough, but there is a section of the play, near the denouement, when Matthew's character has his hands round my throat as he growls, "SAY IT! SAY IT! SAY THE FUCKING WORDS..." And as my character and I struggled to remember what the next words should be, I think there were occasions where Art and Life became a little blurred...

But once the previews are done and the press have spread their love and bile (yes, Charles Spencer, that means you), and the flowers have wilted and the cards are curling and brown against the lights of the dressing table, I have no experience of a long West End run, and what differentiates a Tuesday in March from a Saturday Matinee in May...

The greatest discoveries are the hilarious social experiments to be perpetrated with the random people who turn up to and come out for a drink after the show with me and each other in the upstairs bar at Rules. Friends and family, actors, teachers, acquaintances and employers, three high court judges and my accountant have all shared a glass of pinot grigio sometimes unannounced and sometimes in surreal combinations.

The first preview was a corker. My priest, my mother and my producer in the same night... OK, that is exaggerated for effect. My priest is in fact a man I met at an airport. I was waiting in a queue at Heathrow to fly to Rome for a wedding, and in front of me was a bunch of handsome young men of about my age and I started talking to one of them. It emerged that this was his last day of freedom before he went to the English school in Rome, taking the first step to towards holy orders in the Catholic church.

I banished fantasies of being his last shag before a lifetime of abstinence and thus began a long friendship that has now spanned 20 years. It began in pen and ink, and has recently become distinctly one-way, as I haven't set an ink pen to anything in years, and this faithful friend has come to every show and movie and sent me every birthday card from Lourdes, and I haven't been to mass since I went to Brompton Oratory with Bobby Shriver in the early noughties and sat next to Bono. ANYWAY, my priest-friend HAD to come to the first preview because he was giving up theatre for Lent and this was his last gasp – appropriately enough to a show that comprises references to buggery, incest, adultery and murder.

My mother is no exaggeration, and she came to the show with her best friend from the convent, a colourful barrister who recently made her TV debut as the judge on Sex in Court, where couples with a sexual grievance against their partner seek a judgement from my mum's best friend in a kinky version of Judge Judy. My mum's friend firmly believes that she either conjures up or hallucinates priests, so when she saw my old friend from the airport shuffling along the same row in a dog collar she had a nasty turn.

Knowing who is "in" carries huge significance for actors. Some do not want to know and must not be told... rather like actors who cannot bear to catch a glimpse of themselves on screen or hear their own voice, they lose the suspension of their own disbelief and the whole house of cards collapses.

I like to know... anything I say beyond this point opens me up to castigation from performance purists. If I say that I like to imagine that person connecting with a particular moment, line or event in the play, the Purist could say that I should be absorbed in the truth of what I am doing, not on any level conscious of performance. But I am afraid I am not built that way. If I were trying to score points I would try and patronise the Purist by saying I am altogether more Brechtian in my approach.

Alexandre Desplat came to the show early in the run – he is in London to compose and record the music for the final Harry Potter movie. I first met him at the Berlin Film Festival, at the premiere of The Ghost, a film I made with Roman Polanski. Alexandre wrote the music, which makes such an impact on the film and the viewer, it is honestly another character in the movie. I had, in the customary Williams way, invited my entire and extended family to the event. My relatives were doing their best to drink the bar dry at the after party and were conversing freely with anyone who'd listen. On my way back to the bar I heard my cousin, an estate agent and mother of three, say to Alexandre, this tall, dark, aristocratically handsome Frenchman: "But you're so famous, why would you want to talk to me?" And he answered with impeccable gallantry, but not a hint of lechery, as if mystified that she could not guess the answer: "Because... you are a woman..." That last word lingered on lips with infinite pleasure. English men, take note. That's the way to do it.

Jenni Murray came to the play, then interviewed me on Woman's Hour. I was rather wrong-footed when this monolith of feminism asked me if I had a Snog Book, and who was in it, and I hotly denied that I had any such thing. But the fact is I do have a collection of production photos in a single album from a surreal period of my career when I notched up a rather impressive bunch of co-stars all of whom I was required to snog – purely in the line of duty, you understand. Someone who was privy to the album spotted that it features three Bonds: Lazenby, Brosnan and Craig – although I was playing Daniel Craig's mother, so it was more of a hug than a snog. As Annie Reid pointed out on our first day of rehearsal for Happy Now? at the National, "Who'd have thought? You might have played Daniel Craig's mother, but I shagged him."

It is tricky to know how to react when the teachers from my daughters' C of E state primary school see the play. I conclude that I will be the more embarrassed by the content of the play, and that if they have been warned, it is up to them to decide.

I think their curiosity was nudged by the fact that my younger daughter announced that she wanted Matthew Fox to be the object she brought in for her Show and Tell. I had to check with the staff that a human Show and Tell was permitted, and they felt that on this occasion, that would be fine. Matthew agreed and so at the appointed time, Roxana presented Matthew to the class. She described him as an actor and an American, and that he worked with her mum, then opened the discussion for questions from the assembled four-year-olds, who, when they can't think of a question, have a back-up question or two.

"Did you get it for your birthday?" To which the answer was no.

"Did you choose it or was it a surprise?" A surprise.

"Do you play with it at home?" A nervous look at me. I shook my head. No. We don't play with it at home...

The teachers came to the play, and seemed entirely unperturbed by the content, or by the fact that we were all going to be doing the school run in a few hours' time, and downed a good few glasses of wine before the management of the fashionable West End bar begged us all to go home, as it was closing time.

'In a Forest, Dark and Deep', Vaudeville Theatre, London WC2 (0844 412 4663) to 4 June