Frances Barber plays Princess Margaret in The Queen And I...

Tell us a bit about your character and how she fits into the story. Does she find it hard to adjust?

In an odd way, she probably finds it easier to adjust than any of the others, because she's not really quite sure what's going on. As we know, Margaret loved a drink and a smoke, these days we have her vaping, but she's always got a gin and tonic in her hand. And she's just sort of permanently confused, well, that's how I tried to portray her, anyway. And the script encourages me to do that, in that she's: "Where are we? What are we doing? Oh, sis always sorts it out."

My favourite moment is: Princess Margaret was always on Mustique wearing kaftans and turbans - so there is a moment where I'm vaping on the doorstep wearing a kaftan and a turban, perfectly happy. She's got a gin and tonic and her vape so she's actually quite content.

Was she a fun character to play?

Oh god yes. I loved her. Princess Margaret did a Desert Island Discs not long before she died and every time I thought I was overdoing the accent, I put it on my headphones and thought, no, no, no, I'm not even near where Margaret's accent was. Her Desert Island Discs I'd recommend to everyone because it's all marching music - the thing Princess Margaret would have had on a desert island is the highland bagpipes. I played it to Amanda Abbington in the make-up room and we were howling.

Did you draw anything from real life to help portray the sibling relationship with the Queen?

I've known Sam Bond all my life. We've been friends since 1980, or something. So it was very funny being able to work with her again with all of that history that we have between us.

Every time the Queen told me off I'd just stick my tongue out at her behind her back. I don't think Sam knows I've done that. I'm not sure if she's going to be happy or not with that bit, if they keep it in. I'm sure that [for] Margaret - a bit like Harry now - it was much easier to have the role of being the princess that did not ever have to be the queen and therefore could just be more relaxed about what she said, how she behaved, her friendships, her lovers... Whereas the Queen never had that option, so I think life must have been a lot easier for her.

What was the shoot like?

It's one of those jobs where you genuinely pinch yourself and think, is this really work? How could you not have fun with that cast? It was truly one of those great jobs that don't come up very often. Interestingly, on the street where we filmed, I played Bob Hoskins' wife in an episode of The Street, written by Jimmy McGovern, all those years ago, so that was very weird for me to go back dressed as Princess Margaret.

You've done both comedy and drama, and this has a mixture of both, do you prefer one or the other?

I think comedy is really, really difficult - for me - it doesn't come naturally, it's not the world that I have inhabited. But I've done quite a few comedy roles now, in things like Psychobitches and Friday Night Dinner. This is a combination of drama and comedy, but the reason things are funny is because they're truthful, so that's what we tried to do, we tried to play the truth of the ludicrous situation, but within the confines of our characters, and hopefully people will find it funny.

How do you think the public would react if the monarchy really were abolished?

I think they'd react in the way they suggest in the film. I think the monarchy is beloved in this country, far more than people give it credit for. I'm a huge monarchist and it's not very cool to say that, because, you know, the cool kids think that it's overrated and it's gone, but at the moment, particularly in the crisis we appear to be in the middle of, it's the one thing that we've got to hold on to. I personally think The Queen is extraordinary and what she's done for the country is fantastic.

It has evolved. The idea that the two princes talk about their mental health issues because of the death of their mother was a huge step forward to connect to the public in a way that never happened in the past. I love them, and I adore Harry. He's become someone I think younger people have really taken to their hearts, actually.

Do you think you'd like to be a member of the Royal Family in real life?

Oh god no. Can you imagine? No, it must be hell. Also, people think they don't work hard, they do! They are doing engagements hour, after hour, after hour. When the public realise how much work they do behind the scenes I think they appreciate it.

Do you think the story says anything about class in Britain?

I think it definitely does, and what's quite moving about it is, at the end, The Queen appreciates the love and support that this so called lower class has given her when she's been in an impossible situation. She makes a terribly moving speech in which she says that she feels as if she's learned something about communities and families and opening up and genuine support.

I think Sue Townsend hit upon something, in that the monarchy is 'The Firm' but it's also a huge family. When they do mess up, because all families do, those things have made them more beloved in the public's eyes, because they're seen to be human. I think if the film is trying to say anything at all, it's that. They're actually just human beings with all their foibles, and all of us are battling those every day, aren't we?

And what do you think the Royal Family's Christmas is like?

Well, again, I think they work really hard. I presume they do have a lovely family experience. I mean, who knows! I would love to be the invisible woman watching... because I'm sure there are arguments. Who knows what presents they give each other. It is endlessly fascinating. It's like a soap opera that will never end - one hopes. We're all, I think, rather mesmerised by them. I think it's wonderful that Harry has married a woman of colour. It's given an entirely different modern approach to the monarchy. It's all going in the right direction as far as I'm concerned.