"Character actor” is one of those strangely meaningless terms that’s thrown about all over the place … don’t all actors play characters?

Just as the “world music” catch-all refers to anything that isn’t Western in origin, it’s a label usually stuck on the back of anyone who isn’t quite lantern-jawed lead or doe-eyed starlet material.

But the quite fantastic Alison Steadman – who’s been given this particular tag more than most – is really rather happy with the description.

“I take it to mean that I don’t just play a slightly different version of myself each time,” she says, with the most delicate whisper of a Liverpudlian accent.

“Some naturalistic actors are absolutely wonderful at playing a version of themselves in film and television, and I’m not saying there’s anything wrong with that. But to me, variety is the spice of life and I like to be able to play very different kinds of parts. Look at Beverley years ago in Abigail’s Party – she was totally different to the way I am – and Nuts In May was different again, even though they were done within a few years of each other.”

It was these roles with director and former husband Mike Leigh (the couple had two sons before divorcing in 2001) that first showcased Steadman’s chameleonic talent; her sensational portrayal of the eponymous, Demis Roussos-loving dinner party doyenne in Abigail’s Party created a gay icon and a character so convincing that plenty still believe the actress is from Essex.

Roll forward to today and she’s made dozens of roles entirely her own in Life Is Sweet, Pride And Prejudice (the 1995 adaptation is still thought the best) and most recently in the BBC’s comedy gem Gavin And Stacey.

On Tuesday she reaches Brighton in Blithe Spirit, playing alongside Robert Bathurst, Hermione Norris and Ruthie Henshaw in Noel Coward’s tale of spectral silliness. She croaks a little as she speaks down the line to us after a long day of rehearsals.

“It’s quite tiring, you know … Noel Coward is a brilliant writer, and with the really good ones you’re more anxious to make it work and get it right. We’ve all been working very hard and feeling very nervy about it all coming together.”

That such an experienced and cherished actor should be having a little wobble might come as a surprise to some, but Steadman is hardly unique in this; her good friend Brenda Blethyn admits to near-crippling nerves before every stage performance and it seems having decades of performances under one’s belt doesn’t necessarily make the next one any easier.

“It’s a hell of an ordeal getting on-stage with a new production.

The first few performances are always extremely difficult. And make no bones about it, there aren’t many actors who can say they’re perfectly calm.

Of course, you don’t show it – or hopefully you don’t!

But the older you get, the more you know the pitfalls, the more people expect of you, and so the burden gets heavier. It doesn’t get any easier as the years go on.”

Steadman plays Madame Arcati, the medium whom novelist Charles Condomine invites to his home to perform a seance, and who inadvertently summons his departed first wife. Steadman says Coward has “pulled off a real gag here” in that his characters are convinced of Arcati’s fraudulence, yet she does deliver the goods. Would she be taken in? “I don’t believe in the spirit world at all – not for a second,” she says, without hesitation.

“I’d love to believe there were people floating around and sending us messages, but I’m quite cynical about all that. That’s not to say that kind of thing can’t be fun, though.”

It was with this very purpose that Coward went about writing his unashamedly gigglesome play, as Hitler’s bombs fell on London. His own office and apartment had been obliterated in the raids when Coward decamped to Snowdonia to dash out Blithe Spirit in five days, and there’s something rather apt about this morale-booster being revived as a pall of economic gloom hangs over Britain.

“It was written to raise spirits, so if we can make people laugh and make them forget their troubles for a while, then why not?” Steadman says.

She’s no stranger to comic roles, of course, and in many of her creations, from Abigail to Gavin And Stacey’s Pamela Shipman, she’s been at her best in utterly believable but frequently excruciating situations.

“I think the essence of comedy is that we love sitting in the theatre in a warm, safe seat saying ‘Oooh, I know that person, I understand that situation’, or ‘I’m really glad that’s not happening to me’. We can see life reflected and feel empathy, but we know they’re actors and it’s not real.”

It’s as Pamela in James Corden and Ruth Jones’s sitcom that Steadman has become known to an entirely new generation of comedy fans, but despite speaking with genuine affection about the family atmosphere within the cast, Steadman is glad Gavin And Staccey ended on a high rather than a whimper.

“You don’t want a show like that ending with people saying it’s not as good as it used to be, or that there was one series too many – how many times have we heard that? Having said that, if they were to come up with a special at any time, I’d be ecstatic. I miss it terribly.”

Steadman has always chosen her parts in a rather unconventional fashion, but one that makes a strange kind of sense when one considers how distinctly each of her characters speak.

“I know if I want to play a part or not by the fact I can hear the voice in my head when I read the script.

I don’t know why that should be, but down the years if I’ve been reading something and I can hear the character in my head I know it’s something I want to do.”

She says she’s fortunate in not having seen either a production of Blithe Spirit, or David Lean’s much-loved 1945 big-screen adaptation.

“It’s meant I’ve just got to do my own thing, because actually it’s mine now. For the next few months, it’s mine, then someone else can have it. So it was nice to be able to hear the voice in that way.”

While Steadman’s hardly struggled to get some of the plum jobs in recent years, there’s long been a belief there simply isn’t the number of roles for older women commensurate to the acting talent we so clearly have. Steadman admits to mixed feelings on the subject.

“Plays and films only reflect life, and life is very concentrated on the young. It’s not always a bad thing, of course – we need to nurture young people and their energy – but we mustn’t forget there’s this huge population of older people. I think we’re slightly out of balance, and it would be lovely to have more people writing with older characters in mind.”

Steadman will be living out of a suitcase until Christmas, of course (the play transfers to the West End in the spring next year), but she says the touring lifestyle is made more bearable in having a partner, Michael Elwyn, who’s also an actor.

“I think if your partner’s in the same business, they’re going to be more understanding whatever profession you’re in. That goes for doctors or carpenters or whatever else, but I think it’s particularly true in a job that’s nerve-wracking and where you work peculiar hours while everybody else is enjoying themselves. So yeah, it’s great to have someone who’s sympathetic to that.”

Steadman, a keen ornithologist, walker and nature lover, plans some time away from any theatres, audiences and cities when the tour comes to a close.

“Come Christmas and New Year I’ll be out there with my binoculars looking for foxes and things. Foxes are still my favourite animals, even if they’ve had a bit of a bad press recently.”

* Blithe Spirit will be at Theatre Royal Brighton from Tuesday to Saturday, November 20.

Call 08448 717650 for tickets.