Sinéad Matthews: Happy-go-lucky and in a world of her own

I'm single. I'm footloose and fancy free!" chirps actress Sinéad Matthews, with cheerful laughter, before adding that it's just as well: the role she's currently rehearsing for – Tennessee Williams's The Glass Menagerie, which opens on Thursday at the Young Vic – is putting her right off relationships. In Williams's four-character play, Matthews plays daughter Laura Wingfield who, crippled by a bout of pleurosis, has withdrawn into her own world.

"The part of Laura – she's so nervous and so awful with those situations that I find that I'm not particularly good at that sort of thing at the moment. I'm a bit hypersensitive around that subject. I don't want to start anything," says Matthews. "Laura has retreated and she's quite happy with being in her own world. It's quite a lonely character."

The role is her latest in a string of theatre jobs, which have included Ibsen's The Wild Duck at the Donmar, and Lulu at the Gate Theatre. It is testimony to how much of a rising star the 30-year- old is, that she is so much in demand – she is already lined up to star in Mike Leigh's 1979 play Ecstasy next year at Hampstead Theatre, the third time she'll have worked with the director.

The actress found herself an early champion in Leigh. Matthews had not yet finished her course at Rada when Leigh started coming to watch all her shows. After he saw her first Rada show, Arthur Miller's The Crucible, Leigh wrote her a note, saying how much he had enjoyed it. "He was very sweet, because I only had a small part, and my hat came flying off as I was running round the stage, which I was rather embarrassed about," Matthews recalls. "But he assured me that even though this happened he still much enjoyed it and would definitely come back to see more of my work. He's completely supported me from the word go."

It was Leigh who first gave the talented young actress the platform where she has proven herself to be an actress to watch. Leigh cast her in her first professional acting role in his film Vera Drake, and she has since starred in Happy-Go-Lucky.

Her current character is somewhat different to the last flamboyant role she played this summer in Lulu. Matthews is lively and open, but she can identify deeply with Laura, due to the stammer she had in her childhood. "I used to be quite nervous and Laura's a very nervous person. I can relate to being in situations and not wanting to be in them. I've slowly grown out of it as confidence grows. Sometimes I still get the stammer and that's fine. It doesn't rule my life like it used to."

As a child she was obsessed with dancing, films and musicals – easier to practise with a stammer. "I was never a stage-schooly person, I was a bit too shy for that – I just loved dancing. Because of my stammer it was a way of expressing myself not through having to talk."

She enrolled at Stratford-upon-Avon College where she took drama classes, and soon realised university wasn't an option – she just wanted to act. Coming from a working-class background where drama school "wasn't possible" (her father is a floor tiler and her mother is a primary school teacher) she had to pursue it with self-belief alone. "When my parents first realised that that's what I wanted I think they were slightly fearful of it. Looking back it must have been a self-belief or else I wouldn't have done it."

This year she turned 30. Does she feel any different? "A lot of people have said they've been really depressed. It's been the opposite for me. I just feel like it's a brilliant thing. Because your twenties are all about making mistakes, exploring and discovering who you are."

Meanwhile, she keeps the advice that Leigh gave her when she was still at drama school: "Never change who you are." "Hearing him saying it gave me faith in who I thought I was or who I am."

'The Glass Menagerie', Young Vic, London SE1 (020-922 2922) Thursday to 1 January