Sue Johnston causes a stir as the Dowager Duchess’s new maid in Downton Abbey (ITV, Sunday) and she tells TV Times about working with Maggie Smith and catching up with old friends.

Did you feel nervous about meeting Dame Maggie Smith?
“I’d never met her and I’m such a fan, so I was shy of her at first. Meeting her was like being in front of the headmistress when you are a little girl and it was rather the same feeling I had when I met the Queen!”

Did she make you feel at home?
“She was fantastic and terrific fun when we had to kill time on location, so it was an absolute privilege. She said she loved my work and left me a lovely card when we finished filming, which was nice, so I felt there was a mutual respect and it gave me more confidence.”

What’s Denker like?
“We don’t know much about her history, but she must be a good maid to have come into the Dowager’s employ. She’s quite a character though, she’s well-behaved with the Dowager, and they form a bit of a bond and an interesting relationship develops, but behind the scenes she’s feisty and not as good as she could be…”

Is there any conflict between Spratt and Denker?
“Spratt is quite grand and Denker thinks she is very important too. They loathe each other, so they’re always trying to set each other up and the Dowager has to step in and stop them like they’re naughty kids. It gets venomous in the end!”

What was it like working alongside your long-term friend Lesley Nicol?
“We’ve known each other for 100 years, but we’d never worked together so it was an absolute thrill.  It was fun because her character doesn’t think that much of mine. Denker doesn’t endear herself to the rest of the household at all!”

Did you relax into your role as a 1920s maid?
“I’ve played maids in the past so I understand the protocol. There’s something wonderful about a period costume too, it changes your physique. You look enviously at the beautiful costumes the upstairs people parade around in though, when you are just in your black outfit, and it was hot wearing stockings and a serge frock when we were filming with the fires roaring.”

As a fan of the show, was Downton a dream come true?
“I’d always thought it would be lovely to have a job on Downton, so I was excited. We are all suckers for a period drama and it’s just so classy with beautifully written, well-considered characters. It came along at the moment when we were all ready for something like it too. It’s like Brideshead Revisited from years ago, which just swept along a whole generation.”

Were you aware of how popular the show really is?
“We were in a churchyard and Jim Carter was giving a speech and there was this terrific noise and a coach had pulled up and all these tourists had got off with their cameras just to watch us I couldn’t believe it, it was extraordinary.”

Would you like to do another series of the Royle Family?
“I’d love it. The Royle Family is a great job and the people are lovely, but it’s down to whether Craig Cash and Caroline Aherne decide to write one. It’s always a surprise when they say that we’re doing another and I go, ‘Yippee!'”

You’re now a grandmother, do you still enjoy working?
“I’m just happy that anybody wants me still to work for them, but I also like being at home because I have the babies. I just had another grandchild recently, so I’m very loved up.”