ROBSON GREEN knows how to make a point. “Last year was pretty dark, Christmas was like: ‘F*** you! Humbug!’ But it was what it was – I was homeless.”

The Northumberland actor’s house was severely damaged by Storm Abigail last December, and he was only able to move back in two weeks ago.

This year, not only will he be home, finally, but things are looking distinctly less humbug thanks to the first Grantchester Christmas special.

Based on The Grantchester Mysteries by James Runcie, the ITV series sees Green play cantankerous Detective Inspector Geordie Keating, opposite actor James Norton’s chiselled, yet troubled, Anglican vicar, Sidney Chambers.

The special, which sees 1950s Cambridgeshire heavily frosted with snow, fills the gap between series two and series three, the latter of which is currently being filmed and due to air next year.

“The Christmas special was a joy,” says Green, 51. “Beautifully written by Daisy [Coulam], it has all the ingredients for the event, and I defy anyone not to cry in the places where you’re meant to cry, and laugh where you’re meant to laugh, it’s a joy, and James is on fine form.”

There is a murder too, of course; a groom goes missing, only to be discovered dead with the wedding rings wedged in his mouth, reminding Geordie of an unsolved murder from almost a decade ago.

But Norton also promises “snow, carols, turkeys, some dodgy Christmas jumpers, more snow, a little heartbreak and a lot of Christmas cheer!”

Series two ended with a very pregnant Amanda – Sidney’s forbidden love interest – leaving her husband and turning to the vicar for support, so it’s no surprise that the heart of the Christmas episode is still a will-they-won’t-they romantic struggle.

“They’re going to do their best, but it’s a really complex situation,” says actress Morven Christie, 35, who plays Amanda. “Given that it’s 1955, divorce isn’t particularly straightforward...” – especially as vicars were not permitted to marry divorcees.

“They’re like magnets, they attract and repel,” says Christie of the love-struck pair. “For Amanda, he’s something around which she orbits, so she can’t ever quite let go because he’s the love of her life, her soulmate, but also her best friend on a day-to-day practical level.”

“It’s typically confusing and complicated,” agrees Norton.

He explains how it’s gradually building towards a point where Sidney must choose between “his faith, his duty to the church, and his love for Amanda”.

“It’s a happy kind of an ending in one sense, but it’s also a, ‘What now?’”

The comedic elements are set to come largely from Sidney’s naive curate Leonard Finch, played by gangly Al Weaver, 35.

“So Amanda’s heavily pregnant and what am I doing? I bugger something up – that’s it, the nativity!” he says with a laugh. “Originally in the script it was like, ‘Sidney? He gets to do everything! He won’t let me do anything!’ [Then Sidney goes] ‘Oh, have the nativity, Jesus, have it,’ – which is weird because Leonard really isn’t good with kids.

“But he’s got this vision, and he’s been reading lots of Brecht, so he attempts to put on a Brechtian-style nativity – with a bunch of four-year-olds.”

Weaver explains the finished result is an “absolute disaster and it’s just me running ‘round like a headless chicken” –which is something to look forward to.

While Weaver just about managed to keep control of his gaggle of child co-stars and slip nine of his family members into the midnight mass scene, he found dealing with the drifts of fake snow far less enjoyable.

“Fake snow and green screens – it sounds more exotic than it is, it’s like burnt stuff which smells of fire and it gets in your nose and your eyes,” he laments ruefully.

The cast and crew had been planning to watch the Christmas special together, but star of the show James Norton admits he has no intention of watching himself onscreen.

“We’ll get very, very drunk and watch it – and hopefully, by the time it starts, we’ll all be asleep, haha!”

The Grantchester Christmas Special, STV, tomorrow at 9pm.