Hugh Bonneville is standing on stage giving directions. But this is not London’s West End or even the set of Downton Abbey where he spends six months of the year as the Earl of Grantham, Robert Crawley.

This is an empty hall at Palmerston North Girls’ High and the British actor is preparing to give a one-off performance to an unsuspecting Kiwi fan.

“I’m really nervous about this,” says Bonneville, who days earlier was rubbing shoulders with Hollywood’s A-list at the Emmy Awards.

The fan in question is 17-year-old student Lauren Hutchinson.

Bonneville, with the help of an assistant, managed to track the Downton devotee to the Manawatu after he noticed one of her tweets online lamenting a lack of excitement in her home town.

“I can understand young people who live in corners of the world where they feel not a lot happens or that no-one listens or whatever,” he says. “It’s just worth occasionally, if you can, saying ‘No, we do listen. You’re one of our viewers – you’re important.”

Most stars might oblige by sending an autographed photo. Bonneville, in the country to promote Downton’s latest series, wanted to surprise her in person.

“I hope it’s going to go OK,” he says of his plan to appear from behind the stage curtain during a school assembly. “I’m going to try my sort of Derren Brown ‘I’m a mystic and I’ve got psychic powers’ and I’m going to gradually reduce the numbers in the room until I get down to a few and then hopefully choose her. It could backfire.”

The principal tells the star not to be offended if some of the students choose to leave after the bell rings.

He jokes that his biggest fear is the girls will be disappointed he is not dashing co-star Dan Stevens (Matthew Crawley) or Michelle Dockery (Lady Mary). Or, worse, no-one will recognise him with a beard (grown for his next TV role; he will play a tramp in Mr Stink, an adaptation of David Walliams’ children’s novel).

We retreat backstage to wait for the hall to fill. Backstage in this instance is a school change room – a far cry from the VIP soirees of the Emmy Awards.

“They know how to party,” Bonneville says of America’s biggest television awards ceremony where he was nominated for Outstanding Lead Actor (he lost to Homeland’s Damian Lewis).

Downton, which last year won Outstanding Miniseries, competed in the much fiercer Outstanding Drama category this time round.

While Homeland also took that prize, the nomination nonetheless confirmed the British costume drama’s place among the medium’s best.

“This year to have been, as it were, promoted to top table and to be amongst those dramas like Mad Men and Breaking Bad and Homeland, which are the big heavy hitters, was great for us,” he says.

Critics weren’t the only ones heaping praise on the show from across the pond.

“There was a bit of a mutual Mad Men/Downton love-in”, Bonneville smiles.

The media does make out that there’s this sort of competition or war between shows, but we’re all just jobbing actors and writers and producers all trying to entertain.

“I couldn’t have been more thrilled when Damian won and to meet some of the guys and writers from Mad Men, who are extremely fond of [Downton creator and writer] Julian Fellowes as well, was great.”

However, Bonneville insists he wasn’t there to hand out business cards.

“I’ve worked (in the US) two or three times and I’ve had varying degrees of enjoyment in the work I’ve done there. But my roots are in the UK. I love visiting (the US), but I can’t envisage moving myself lock, stock and barrel for a long period.

“But you never know, that’s probably what Hugh Laurie said 10 years ago,” he jokes.

While Downton may have missed out on the top drama Emmy this year, the series is certainly not lacking in hardware for the mantelpiece.

When the cast came together for the first script read-through of season three, which begins this Thursday on Prime at 8.30pm, all their recent awards were placed on the table.

“It was rather sweet,” Bonneville says, “Our bosses from both sides of the Atlantic were there. It was a very cold February day and we needed something to cheer us up so (producer) Gareth Neame plonked them all down. I’ll show you.”

Bonneville pulls out his phone and begins flicking through photos.

“Here’s me bringing the Golden Globe back from America – we gave it its own seat and headphones [on the plane]. That’s the National Television Award. That’s my neighbour with her can of beer. Here we go. That’s the read-through.”

Standing proudly on a very long table surrounded by the whole Downton household in casual attire are the Golden Globe, the Emmy, the National Television Award and the Broadcast Award that the show collected for its first season.

Did the presence of all these trophies mean more pressure?

“To be honest, no,” Bonneville says. “These are very wonderful accolades to have, but they are add-ons.

“Once we’re in the freezing cold fields at Highclere Castle at 7.45am on a February morning and you’re chipping the ice off the Winnebago to try and get in, the lovely few occasions of the year when you are on a red carpet and people are celebrating the end result, they seem a long, long way away.”

Producing the end result is something the Downton team take very seriously.

While Bonneville likes to stress that the show is a work of fiction, they are surrounded by a skilled team of historical advisers – from a cook who prepares period-appropriate meals during those lavish dinner parties to the props department.

“If we’re doing a breakfast scene and there’s a newspaper, it’s always the right month and year that it should be.

“There was a moment in series two where we were doing a breakfast scene and there’s a facsimile of an original newspaper talking about how Tsar Nicholas’ family were reported to be shot yesterday and you think ‘My God!’ It suddenly becomes very vivid. It’s not just a blank piece of paper with blah blah blah written on it. It’s actually the newspaper.

“It doesn’t change your performance – I mean, you’ve got 20 people in jeans standing around with cameras – but it informs, it drips into your brain.

“It’s that attention to detail, sometimes we’ve got it wrong, but on the whole, we’re aspiring towards that authenticity – we aim high. Every department aims high and that makes you aim high as an actor.”

The characters, on the other hand, are more prone to slip-ups. Among them, Robert’s almost-affair with a maid last season. Did the actor receive any feedback about his Lordship’s indiscretion?

“Oh yes!” he beams. “A lot of people were furious about that.

“I think that’s one of the great things about Julian’s approach to his characters. He says that, as in life, just when you think you get to know someone, or when you think you understand someone, they surprise you and I think that’s true of every axe murderer who was a lovely member of the community or every bloke who’s made some sort of mistake like Robert does.

“Some people said well, that’s life, that happens, and some people really couldn’t bear that the noble lord was human.

“I thought it was great because I knew it would piss some people off,” he laughs.

“In the same way when people had written off the character of Thomas the footman as just an evil, bad man, I defy anyone not to have started to feel sympathy for him in series two when he became attached to one of the soldiers.”

The son of a retired surgeon and nurse, there was little chance of Bonneville following in their footsteps (“I pretty much faint at the sight of blood”).

The backup plan was law, but when he told his parents he wanted to give acting a go, “To my eternal delight they said, ‘We’re right behind you’.”

“That was 26 years ago or so and I haven’t yet had the tap on the shoulder from them saying go and do law.

“They prefer theatre to TV, of course, because it’s legitimate, but Downton’s ‘sort of allright’,” he laughs.

At least one member of the audience, now taking her seat in the school hall with no idea about the special guest about to make her day, would surely agree.