Tamsin Greig has proved her comedic prowess in long-running sitcoms suh as Green Wing, Episodes and Friday Night Dinner.

But the BAFTA-nominated British actress is about to show off her straight-acting skills in Belgravia, the new ITV period drama from Downton Abbey creator Julian Fellowes, set in 1800s London.

In the six-part mini-series, Greig plays Anne Trenchard , a woman who loves and enjoys the success of her husband James Trenchard (played by Philip Glenister), but who is desperately hiding a secret heartache that could change their lives.

Speaking to BT TV and other journalists at the launch of Belgravia at The Soho Hotel in London, Tamsin Greig discusses what appealed to her about the series, the constraints of wearing a corset for 12 hours a day, and how Belgravia compares to Downton Abbey.

1. What appealed to you about the role of Anne Trenchard?

Belgravia ITV ITV / Carnival Films

I was really excited to investigate a world which the viewers are invited to inhabit through the aorta of a woman. You’re brought into this really rich, diverse, fascinating world, but you go in through the story of this woman, who is caught in so many different ways, in the dichotomy of division. 

She’s not the right class, but she’s there, because she’s part of the up and coming nouveau riche. She has been told by her husband not to talk about this secret, but she is compelled to break her world. 

Really it’s a story about how people live with grief, and I think that’s universal. That may well be one of our greatest problems today, is that we won’t just sit with our grief, and see what happens when we take it seriously. 

2. How would you describe Anne?

In the novel, Julian uses a very brilliant adjective to describe Anne and it’s ‘opaque’. I thought that that was all I needed. 

He also said that she was naturally well-bred, because she didn’t care about being well-bred. There was no concern about social standing, or ambition, which made her well-bred in her sense of self. 

I love the fact that she’s opaque, so she spends most of her energy covering up what’s really going on, whether it’s to keep the secret that she’s promised to her husband that she won’t reveal, or to guard the terrible heartache, she creates a very effective character.

3. What about the relationship between Anne and her husband James?

Anne and James Belgravia ITV / Carnival Films

The relationship is tested, but I think they are more alike than they are different. They do keep secrets from each other, and there’s something terrible about that, but there’s something very honest in the hypocrisy of that - they’re both doing the same sh*t. 

I found a very interesting piece of information when I was doing research for this that around the time they would have got married, there were about half a million more women than men in the country. So it’s not that Anne knew it, but by her circumstances, there would have been fewer men. 

I also get the sense that as the son of a market trader, there would have been a cockiness and bravado [about James] that is possibly quite sexy. I think that Anne probably is quite thrilled by his balls, and punching so far over his weight.

4. Were the corsets comfortable to wear?

I was under the care of an osteopath quite quickly. I think I probably should have prepared myself before filming by wearing a corset for a couple of hours a day before it. 

To suddenly be in one for 12 hours a day is pretty tough because we’re used to being able to move our spines, and apparently for spine health the best thing is to be able to move it, and be able to breathe, neither of which you can do [in a corset]. 

We had a half hour for lunch, and I began to insist for that half hour, I had to be taken out of it, because it was quite hard. It was teaching me a lot about how women are agreeing to be contained.

5. What’s the difference between the corsets Anne wears in the two different time periods?

Belgravia Anne corset ITV

When you have flashback scenes to the [Battle of] Waterloo, that’s a regency line, so the corset is really tight [under the breasts], which means that the waist can be slightly looser, because it’s the empire line that drops more loosely. 

What’s interesting is that when it goes through the century, the industrial revolution is finding its momentum, the men are being separated from family businesses because then they’re going out to work, and the corsets are getting tighter and tighter. 

So in the 1840s you have a very different corset, creating this tiny silhouette, which is trying to replicate a teenager [Queen Victoria] on the throne. They’re looking for a silhouette that doesn’t match most women. So as men find greater industrial and financial freedom, the women were agreeing to be more and more constrained.

6. Is Belgravia similar to Downton Abbey in that the servants have their own storylines?

Belgravia servants ITV / Carnival Films

The servant world feels like a Greek chorus. You’ll get much more of it through the series, then it becomes really rich and vivid, because you see these other lives commenting on the central action. Not just commenting on it, but how they can manipulate the information, and allow it to work for themselves. 

Paul Ritter, who plays the butler, he just has this beautiful line where he says "I’m not a rich man", and you know that’s the whole motive for that man. He gets pulled into ‘what can I do with this information?’ because he knows that his days are numbered. 

It’s not that he doesn’t like his employers, it’s that he’s trying to survive. All those servants are so vividly drawn, because they’re all focusing on that one thing that will keep them surviving. 

7. How were the scenes you filmed with the dog?

Belgravia Anne dog ITV / Carnival Films

The dog was a newbie to the business, so she had a massive trailer and a great agent!

It was lovely to have her on my lap on the cold days. Her real name was Emma, and she was very sweet. She was pulling on that lead, but she’s being fed at the table. 

I love that bit where James says [to Anne] "Get that dog off the bed!" and she just snuggles down with it. It’s such a beautiful way of saying "I hear you, but I ignore you".

Belgravia continues Sundays at 9pm on ITV.

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