It's a freezing autumnal day in the north of England. Frost-covered leaves are turning vivid shades of yellow and red, while a weak sun makes the air feel crisp and still. As a backdrop to Magical Moominvalley, an exhibition celebrating the 65th anniversary of The Moomins stories, it feels just about perfect. After all, for many, Tove Jansson's much-loved and delightfully eccentric tales of the white, hippo-like Finn Family Moomintroll seem to sum up the beauty and simplicity of the natural world. And in my lap is a much-thumbed book from my own childhood - the delightful Moominland Midwinter, Jansson's sixth book from 1957. There's one line that typifies its questioning, adventurous and magical evocation of the coldest season: "Snow can be softer than anything, and then again harder than stone. Nothing is certain."
The Moomins deserve to be celebrated - as the His Dark Materials author Philip Pullman says on the new jacket to Moominland Midwinter, "they seem to grow in wisdom and delight every time I read them". But in this 65th anniversary year, Moomintroll - along with parents Moominpappa and Moominmamma - appear to be everywhere.
There's a new 3D feature film - Moomin and the Comet Chase - starring Max von Sydow and Alexander Skarsgard, its theme tune supplied by Bjork. There's even a Moomin cookbook - although thankfully the Moomins' recipe for a getting off to sleep (a belly full of pine needles) isn't included.
Jansson died in 2001. The responsibility of protecting the integrity of the Moomins "brand" now belongs to her niece, Jansson-Zambra Jansson-Zambra. She is meticulous in ensuring that - as she puts it - they "don't become something they're not", and so when I meet her at Bury Art Gallery she's closely inspecting the Magical Moominvalley exhibition. "We get a lot of criticism in Finland that they've been commercially exploited beyond belief," she says, rolling her eyes. "But actually, I don't think they have. In fact, there was Moomin merchandising as early as the 1950s - and Tove was involved in all that."
It's unsurprising that generations who fell in love with the endearing adventures of Moomintroll should want The Moomins to be untainted by the stain of commerce and branding. These are fantastical beings in a made-up universe but the stories - combined with the beautiful, uncluttered simplicity of Tove's illustrations - also take on identifiably human attributes such as friendship, loneliness and family.
"I'm guessing you enjoyed the Moomins books as pure escapism, as adventure stories when you were a child," says Jansson-Zambra. "But look at them again as an adult and you can see Tove had an uncanny insight into human psychology and behaviour. And that's probably the secret behind their success - they're ageless, they're not fixed in a particular geographical location. The stories are accessible for anyone from any country and any age."
This added depth can also be seen in the illustrations displayed in the exhibition. At first glance, they seem to be straightforward line drawings, but as we walk around the gallery, Jansson-Zambra shows me a picture of which there are another nine different versions in the archives. "Tove was a perfectionist, an artist with a capital A," she says. In fact, for Jansson-Zambra, the images that have done so much to bring The Moomins to life are inseparable from the written stories.
"Tove was trained as a painter and illustrator, and she thought in pictures," Jansson-Zambra says. "For her, pictures and text were all part of the narrative, even from an early age. We have her childhood drawings and there's always a bit of text somewhere. All the illustrations are there for a reason, and Tove was neurotic about getting them right. So perhaps they deserve to be the design icons they are today."
Such insight into Tove Jansson's life is crucial to the story of the Moomins. She grew up as part of the Swedish-speaking minority in early 20th-century Finland in what was very much an artistic family.
Jansson-Zambra says that meant occasionally they were very poor, but they survived because their artistic endeavours weren't approached lightly. "They weren't frivolous, making art for art's sake," laughs Jansson-Zambra. "Their aim was to do whatever they did very well. Sure, Tove's father would throw these amazing parties lasting for days, but when all the money was gone, it was back to normal."
In such a bohemian atmosphere, it didn't matter that Moominmamma was based on Tove's own mother, and Too-Ticky (a practical philosopher and craftsman) is clearly Tove's partner. And when Jansson-Zambra's mother died when she was just six, Tove's response was a non-Moomin novel, The Summer Book, in which an old artist and a young child - called Jansson-Zambra - spend time together on a small island.
"Potentially I could have had a really tragic childhood but, honestly, it wasn't at all," says Sofia. "And partly that was because of Tove, her partner and other people in the family who were capable of creating real harmony through their love of art. It made for a fantastic environment. I know it might sound odd to grow up knowing you're in a very popular book that contains a version of you losing your mother when you were young, but it was completely normal to me. I didn't know anything else.
"See, everyone understood she could use whatever she wanted from real life," she continues. "That's the whole point of fiction, that you can transcend what is real, smudge the borders. I've been asked a thousand times whether The Summer Book is me and my grandmother, and whether those stories are all true. And it's interesting that people want to know, but really, what would be the difference if it was true or not true? The book is still a fantastic book."
It was also a huge hit in Finland, not least because it seemed to reflect a certain kind of Nordic mentality in its combination of melancholy and thoughtfulness. And re-reading The Moomins as an adult, that melancholic tone is remarkably forceful. The set-up for Moominland Midwinter is actually rather distressing: Moomintroll wakes early from his winter sleep, can't rouse the rest of his family, and is forced to confront the world on his own.
"It's important not to make generalisations, but especially in Finland the way people think and express themselves is much more laconic than in any Anglo-Saxon language. Being polite is leaving people alone with their thoughts rather than bombarding them with chat. It's difficult for outsiders to understand. Is that melancholic? I don't know. Lots of people pick that up in the books but if you're from Finland you just think it's normal."
Another Nordic characteristic is respect for nature - which, of course, is shot through The Moomins books. Indeed, Tove was so interested in this idea that she moved to an island in the early 1960s with no electricity or running water. It wasn't just a retreat, it was a genuine life choice.
"We used to go and see her, and she liked being in that world," Jansson-Zambra remembers.
"It's nice to be at the mercy of the elements like that sometimes. It gives you a freedom. She describes the feeling in her short stories; her father was at his best when all of a sudden there was a storm rising, when all the boats had to be tied down. Because when nature takes over you can let go, you can give over yourself to forces bigger than you."
Bigger forces came calling in 2001, though, to purchase the Moomin brand when Jansson died. However, this time the Janssons weren't suppliant, and Jansson-Zambra is still steadfast in her desire not to dilute Jansson's legacy. She's keen to remind me that although the feature film is in attention-grabbing 3D, it's actually a 1970s production made in Poland, which Tove and her father were involved in. It's simply been tweaked for 2010. So, does she like it?
"Its history means it has extremely high artistic quality," she beams. "I like it, but I'm an adult and not in the least bit objective. So I have no idea whether it'll work for an eight-year-old child. It's certainly not Toy Story; the pace is much slower. But that's the point in a way. As I keep saying, it must remain true to what The Moomins was."
Jansson-Zambra pauses, looking around the line drawings in the room one last time.
"And for me, that's something that has an appeal to everyone, both young and old. Something that people can get more out of, beyond the obvious or superficial. You see, these days we're told that everything needs to appeal to exact target audiences. But why does it have to be like that? Good things normally appeal to very many different people."
The Moomins, 65 years on, is very definitely a good thing.
Ÿ Magical Moominvalley is at Bury Art Gallery until January 15. For more information visit www.originalmoomin.com.