Scheming lady’s maid Miss O’Brien is the character viewers love to hate in Downton Abbey but she’s a million miles away from Benidorm star Siobhan Finneran, who plays her. Acid-tongued footman Thomas (Rob James-Collier), her confidante in series one and two, turns against O’Brien in series three when she tries to secure her nephew Alfred a position below stairs and the relationship sours as Siobhan explains…

What can we expect from the dastardly duo?
They’ve fallen out of love with each other a bit which is sad but has been good fun for me and Rob [James-Collier] to play. They’ve been totally devoted up until now but the cracks are beginning to show between the two of them. I wish I could say that she and Mrs Patmore become thick as thieves but, no, sadly for her she’s completely on her own.

Do you and Rob James-Collier have fun filming those bitchy scenes?
We laugh too much and we’re both Mancs — Rob was brought up where my mum’s from — so we have a similar sense of humour.

Is it ever a problem filming Downton Abbey and Benidorm at the same time?
We shoot at different times of the year and we’ve only had one crossover last year, when I had to come back from Spain for a week to shoot more of the Downton Abbey Christmas episode. I’d been in Spain for about two months and they painted me grey before putting my make-up on because I had a tan! You can’t avoid it in Spain, you can’t hide in a cupboard.

Which is the better costume — the Downton Abbey corset or the Benidorm bikini?
Literally anything is better than having to wear a bikini. I’d love to say I go on a really strict diet and fitness regime but I would be lying so badly. I just hope I can tuck my stomach into my bikini bottoms when I get there! But as [Benidorm co-star] Steve Pemberton says, everyone’s seen it all now, there no point in us worrying. The Downton Abbey corset doesn’t actually bother me. Some of the girls say it’s uncomfortable but I think if you have flesh on your bones it doesn’t dig in.

Which character do you prefer, Miss O’Brien or Janice?
It’s too difficult, I love playing both. If you asked me where I prefer working, I would say without question in the sunshine in Spain!

Do you get recognised often?
Not often actually. No one bats an eyelid in Manchester but down in London I’m clocked a bit more. Do you remember the old Harmony Hairspray ad — is she or isn’t she? I’ve had a few of those moments on the tube! People tend to say, ‘Oh you’re not as fat or as ugly.'

That’s very rude, how do you deal with it?
You just put a grin on your face. For them, they’re paying you a compliment, they don’t realise it’s also a bit of a slap. It usually makes me laugh.

What’s the best advice you’ve ever been given?
Don’t wait to have your kids. A lovely actress said that to me who was in her 40s and had kept putting off having children for the sake of the next job. She said, ‘When you get to 60 or 70 you won’t be thinking, "I really wish I’d taken that job," you’ll just be very pleased you’ve got family around you.’ I’ve been broody since I was about seven so it wasn’t really advice I needed but I did take it on board.

ITV1, Saturday

Mary Comerford