Anita Dobson: Angie doesn't live here any more...

It's 14 years since she left 'EastEnders'. So will a stint at the National Theatre finally see Anita Dobson taken seriously, asks Veronica Lee

Anita Dobson is graciousness itself when we meet at the National to discuss her latest role in Bryony Lavery's Frozen. At the last minute, she changed the time and venue of our interview, and as I made a mad dash across town, the image of an irascible luvvie loomed into mind. But Dobson is full of apologies: unreliable rehearsal schedules, not temper tantrums were to blame, it seems.

All a far cry from Angie, the self-centred, booze-soaked pub landlady she played on EastEnders in the role that made her famous, and also a million miles from Nancy, the character she plays inFrozen. It's a harrowing play to watch: a mother of a missing child confronts the serial killer who may have murdered her daughter. Dobson is revisiting the role that she created in the original production at Birmingham Rep in 1998, with actors Josie Lawrence and Tom Georgeson, plus director Bill Alexander – all of whom reunite for the play's National outing. "It's a really great piece to revisit," says Dobson. "I am very grateful for another go at it because it's a very fine piece of writing."

Dobson, 53, is childless herself, so where does she think this character's responses come from? "This situation is unthinkable for a parent anyway," says Dobson. "Because losing a child goes against the natural order. I have stepchildren – the youngest is now 15 and I have known her since she was a toddler. I can only feel that it's like every moment's fear I've had when my stepdaughter, or my niece, or a friend's child that I'm looking after, goes out of sight for a moment, and multiply that by a hundred or a thousand times."

Does she "get" the play's theme of redemption – that a mother would actually seek to forgive the man who may have murdered her child? "I truly don't know, but I can tell you this," says Dobson. "When we did the play in Birmingham, we had a mother of a murdered child come to the play and she told us she absolutely identified with my character. She had wanted revenge but knew that she had to move on from that hatred to save herself. I think it's entirely possible that when Nancy goes to see this serial killer, she might want to kill him, but she knows the next step for her is to resolve things. Once she unblocks the tears, she can start to feel again. She's no longer frozen."

It's with some trepidation that I bring up the subject of EastEnders, which Dobson appeared in from 1985-1988, as it must be galling for an actor to be so defined by one role, however magnificently performed it was. Lavery says Dobson is probably sick of talking about EastEnders but is far too polite to tell people to piss off. I tell Dobson this and she rocks with laughter.

"Oh, that's so nice, but so untrue! I am very glad I did EastEnders and I'm flattered that people still remember me in it. Angie was one hell of a character and I sort of feel she was waiting for me – I knew her from my childhood in the east end and from my years as a barmaid between acting jobs, and I certainly knew men like Den. She was tough and she was a survivor."

While she has gone back to Frozen, she turned down the chance of going back to the soap. "I'm glad they killed Angie off. Her death has been a great closure to that section of my life. Now I can be Anita Dobson." Since leaving EastEnders, Dobson has done some so-so TV, but her theatre work has received accolades from the critics. She has proved she is a great character actress who can turn her hand to Chekhov and Marivaux, to panto and the The Vagina Monologues.

But has she noticed a whiff of that industry condescension in moving from soap to serious? "I have to say I have," Dobson replies. "To some degree it may be my perception, but there is slight degree of 'How dare she be at the National Theatre when she's a soap queen?'. But I think this is also the media putting people into boxes. If you're a good actor you should be able to do soap, comedy, Shakespeare, musicals, pantomime and something like Frozen. Of course, you will be better at some things, but who says you can't do them all? The intent should always be to stretch yourself and broaden your horizons."

Dobson, who spent a decade after graduating from drama school as a jobbing actor and musical performer, released a version of the EastEnders theme tune, "Anyone Can Fall In Love", in 1986 and was pilloried by the press. But she is unrepentant. "Are you kidding? I was appearing on Top of the Pops when I was in my mid-thirties or something. It was fantastic! But it was the weirdest thing, I'll admit. Was I me? Was I Angie Watts? Was I me as Angie? I didn't have a clue, but I was having enormous fun all the same."

Her husband, Brian May, has recently made a successful debut as a West End theatre writer and producer with the Queen musical We Will Rock You. Do they have plans to work together? "We worked together before on an album – years ago – but what Brian does is rock and I'm not a singer: I'm an actress who can sing and that makes a big difference. If it was something where I could be giving a bit of 'me' as the character on stage, then yes, maybe we would go for it."

'Frozen': NT Cottesloe, London SE1 (020 7452 3000), previewing, opens Wed, in rep to 10 August