Michael Rosen and Raymond Briggs – the men putting the heart into this year's festive TV

“I picked it up in the 1970s,” Rosen says of the chant long used in communal singalongs. “In the early 80s, David Lloyd, the boss of Walker Books, saw me performing it and said, ‘That would make a great book.’ I said, ‘Yes, it would!’ He said, ‘You should write it down.’ I said, ‘You do it!’ He said, ‘No, you do it!’”

Happily Rosen did do it. The song became an extended poetic journey in which five siblings – one of whom is a baby no sane parent would allow out of sight – and the family dog go looking for a large brown bear. On the way they encounter various natural obstacles – mud, water, trees, snow – all of which they meet with the rhyme, “We can’t go over it. We can’t go under it. Oh no, we’ve got to go through it.” It proved to be a magical formula. Twenty-seven years later, We’re Going on a Bear Hunt has, by Rosen’s reckoning, sold more than eight million copies worldwide and will surely win more hearts this Christmas.

Raymond Briggs essentially invented the Christmas family animation slot in 1982, when Channel 4 broadcast The Snowman – released with a soundtrack featuring Walking in the Air, sung by chorister Peter Auty (not Aled Jones – he sang on the 1985 single release), to world-shattering effect. However, 82-year-old Briggs is not feeling particularly festive when we meet at his Sussex house in the lee of the South Downs. He’s struggling with an iPad that refuses to play the rough cut of his new film. “It drives you mad,” he says, jabbing an ink-stained finger at the screen. “I’m really going to smash this thing one day.”

For all the charm of Bear Hunt, Ethel & Ernest is undoubtedly the major animated work of 2016, delivering a big slab of British social history via the long romance of Briggs’s parents, voiced by Jim Broadbent and Brenda Blethyn – a suburban girl in service and the street-savvy London milkman she meets in the 1920s and marries.

We see the couple dote on the only child who carries all their hopes, but to fulfil those hopes the boy must leave his parents’ milieu, as Briggs did when he passed his 11-plus. “All my mates from around the corner didn’t get into grammar school,” says Briggs. “I was the only one that did. I didn’t like the feeling at all. I didn’t feel superior to them, but they obviously felt slightly embarrassed. In Ethel & Ernest I have my dad say, ‘I hope he’s not going to get too posh for us.’”

Visiting the production was a testing experience for Briggs, particularly when Broadbent and Brenda Blethyn re-created his parents’ voices. “I spent two days in tears,” he says. “It was just as if they were behind me in the room, saying all the things they used to say.” His parents died in the 1970s, but they lived long enough to see their son’s career established – although his mother wanted him to be a manager. Briggs still lives among their possessions, which can be seen in the animation. He shows me the bread board his mother used, still bearing the marks of her knife, and the wall mirror his dad brought home balanced on his bicycle.

He has been on his own with the bread board, mirror and his many, many books since Liz, his partner of more than 30 years, died in October last year. “I was working on this book about old age and death,” he says. “Liz had Parkinson’s, that led into dementia and then she died. I never got back to it really.” As if to ward off dementia, Briggs has written on the doorframe in black felt tip the words he doesn’t want to forget: prostate, orthopaedic, solipsism, migraine, vascular diabetes, nuthatch and, finally, the actor who plays his father, Jim Broadbent. “I’m all right,” Briggs says, as I eye the list. “I don’t think there is anything particularly bad. It’s just words you know perfectly well, but there are times when I want to say them and I can’t bring it out.”

Thanks to the start grammar school and his parents gave him, Briggs has an unparalleled career behind him. Ethel & Ernest feels like a paying of accounts to two people he owes so much. Rosen, a socialist, is also grateful to the state that educated him for free. He joined the Labour Party when he was 14 and he is a friend of Jeremy Corbyn. When he was made children’s laureate in 2007, it was Corbyn who stood up in the House of Commons to congratulate him.

Which is why, perhaps, Rosen is guarded when I ask just how rich the eight million sales of Bear Hunt has made him. “For plenty of those sales,” he says, “I’m getting much less than two and a half per cent.” That’s still hundreds of thousands of pounds. “There are no rules on the left saying you can’t sell your labour power and get a good price for it. And I spend a lot of time doing stuff that I get no money for at all.”

Like Briggs, Rosen has also encountered tragedy. In 2004 he published Sad Book as a reaction to the death in April 1999 of his 18-year-old son Eddie from meningitis. Rosen is still a busy parent of four. “I’ve got an 11-year-old and I’ve still got two young ones,” he says of his childcare. “I go right up to 40.” Sad Book was illustrated by Quentin Blake, and that is the clearest difference between the authors. Briggs is a master draughtsman who went to Slade School of Fine Art in the 1950s. Rosen writes and performs, and he repeatedly praises his collaborator on Bear Hunt, the illustrator Helen Oxenbury, although their relationship didn’t have an auspicious beginning.

“I gave her my words,” Rosen says, “and I didn’t hear from the publishers for about two years, and then they asked me in. I looked at the first picture they showed me and I thought, ‘What does this have to do with anything?’ Because I had been performing it in the way that you perform if you had to entertain some kids. I didn’t get it. The genius of this book is that I didn’t get it!”

We're Going on a Bear Hunt airs on Christmas Eve at 7.30pm on Channel 4
Ethel & Ernest airs on Wednesday 28 December at 7.30pm on BBC1