Joanna Harrison is surveying the chaos of her London studio when we speak, surrounded by the 200,000 drawings used to make the new version of The Snowman. As art director and co-writer, she took on the enormous responsibility of creating the next instalment of the beloved Christmas film that so captured our hearts 30 years ago, and has been shown on TV every Christmas since.

The Jericho resident is understandably fairly exhausted by the entire ordeal, now that The Snowman and the Snowdog is done and dusted and being aired on Channel 4 this Christmas Eve, but she’s also “enormously proud” of the finished product and can’t wait to see everyone’s reactions.

“It’s been crazy,” she says, “We worked over the weekends and I’ve had three days off since it began. I’d get the X90 up to London, leave at 6am and get back to Jericho at 7pm. But to be honest we were just delighted to get the film finished in time because there was one point where we didn’t think we’d manage it.....”

Joanna admits that since being involved in the first Snowman, she’s been secretly hoping for a sequel all these years: “It appeals to the child in us all,” she says. “It tied in with the 30th brithday of Channel 4 and The Snowman so when we got funding and Raymond caved in we were amazed and delighted.”

Eighty illustrators and artists were involved in the finished product, 12 drawings being needed for every second of action in the 24-minute film, and it was all hand drawn. “That’s what I’m most proud of, because people thought we were crazy and called us Luddites. They said that it couldn’t be done nowadays, and we proved them all wrong,” Joanna smiles.

But why take on such a mammoth project when technology has moved on? “It seemed like selling out otherwise, even though everyone said there was software we could use. But I knew we could, while moving forward to a more refined, defined look to suit HD TV, so we used Caran d’Ache pencils instead of wax crayons because their scratchiness just wouldn’t stand up today.”

Apart from proving them all wrong, Joanna also had the enormous responsibility of co-writing the new story. So did she have a few plots up her sleeve? “No, we always hoped there would be another story waiting in the wings, but still had to sit down [with fellow co-writer and director Hilary Audus], and say ‘how are we going to do it?’, because there were so many stories we could have told and so many directions that James’ life could have taken. So we sat in Hilary’s summer house and just hammered it out.”

Did Joanna go through endless different drafts and scenarios before settling on the right one? “Yes, we even had another story written before we discarded it and decided on this. And although there were a million possible stories, we wanted to base it in the old house, and we wanted a flying scene. And you have to make the audience cry, because that’s true to Raymond Briggs whose work always has elements of sadness, and addresses life and death.

“But our main objective was to move forward while being true to the original. So we purposefully didn’t make it too contemporary because that dates it fast. We made the film as timeless as possible without mobile phones or anything in it.”

Even so, the responsibility of taking on one of the nation’s favourite films for its sequel is a huge responsibility. “Absolutely. We were utterly and completely terrified,” Joanna laughs, “because people so love Snowman, but I don’t see the Snowman and The Snowdog competing with that. So though Snowman was a perfect animation and I love it to pieces, this is different.”

A documentary about the making of the film is aired on December 30, as well as featurettes on New Year’s Eve, so there’s more to come.

By then Joanna and her family will be long gone, tucked away in France for some peace and quiet.

“There has been enormous media publicity surrounding, so I do need to get away for a bit,” she agrees. “But overall we are proud of The Snowman and The Snowdog and bringing back all those skills. It’s been a fantastic experience and I just hope people like the film and that it entertains people for half an hour at Christmas.”