As the benign squire of Downton Abbey, Hugh Bonneville has become the recognisable face of traditional, tea-and-scones Englishness; people who stop to snap selfies with him in the street, he says, are surprised to see him without a dog. Now it would be hard to imagine anyone else as Mr Brown, the buttoned-up paterfamilias who gradually succumbs to the charms of Paddington Bear in Paul King's beautiful new film – because nothing, in the end, could be more English than this story of a bear from Peru.

It is not easy to like Mr Brown. He is in a hurry at the station and does not want his children distracted by a dubious-looking bear spinning some nonsense about being homeless. Even once he agrees to Paddington staying for one night, he is gruffly concerned with the risk of bear-damage and warns his children to lock their bedroom doors. An Englishman's home is his very private castle; the fact that Paddington is a talking bear actually doesn't interest him. "Hugh's first reaction to Paddington is 'stranger danger'," director Paul King – who, as the longstanding director of the Mighty Boosh, comes from a comedy background – told Empire magazine. "He's more worried by the idea that this person might try to sell him the Big Issue, or that he might be a charity mugger, which is actually what London people fear more than anything,"

It is a very different sort of reception from the one promised by the English explorer who stayed long ago with Paddington's aunt and uncle (Michael Gambon and Imelda Staunton) in the Peruvian jungle. From him they learned that British life revolves around good manners and the ability to talk at length about the weather. If you come to London, the intrepid and gentlemanly Montgomery Clyde (Tim Downie) told them, you can expect a warm welcome. "That is his expectation, but of course in reality, as we all know, that is not necessarily the case," Bonneville says drily. "He meets the best and the worst of British manners when he gets here."

The neighbours' curtains twitch when the Brown family arrives home with an unknown guest. Paddington is undeniably well-spoken (by Ben Whishaw) but equally undeniably fur-skinned. Their teenage daughter Judy (Madeleine Harris) is horrified by Paddington: having a illegal immigrant in the attic is "weird" and "embarrassing" although her brother Jonathan (Samuel Joslin) is young enough to be excited by just about anything out of the ordinary.

And while Mrs Brown (Sally Hawkins) and the Browns' formidable housekeeper (Julie Walters) are ready to embrace the interloper, Paddington's sharp ursine hearing picks up Mr Brown explaining that he just doesn't belong with them. Worst of all, Paddington is being pursued by a sinister taxidermist (Nicole Kidman) whose lines of persuasion are all too familiar. "Let one bear in," she hisses at the Browns' malicious neighbour Mr Curry (Peter Capaldi), "and soon the street will be full of them… having all-night picnics!"

This is clearly not the real London. Where a talking bear is no more than a curiosity, we are in fantasyland – but, as Bonneville points out, so is Downton Abbey. At the same time, Michael Bond's original stories carry emotional heft because, underneath the whimsy, there was always the grim consciousness of real-life events. The first of the Paddington books was published in 1958.  "Michael Bond has talked explicitly about the fact that the inspiration for Paddington was the evacuees on the railway stations of wartime Britain who were looking for a home after being displaced," Bonneville says.  Paddington inherited his suitcase and his identification tag (the famous line "Please look after this bear. Thanks" hung about his neck) from the children Bond saw on newsreels.

Bond was 19 when the war ended. He went to work at the BBC monitoring service, which was then staffed almost by refugees from Eastern Europe who inspired his antiquarian character Mr Gruber, played in the new film by Jim Broadbent. "It is a film that is ultimately about people of difference, people from different places coming together and wanting to be accepted," Bonneville says.

For Sally Hawkins, the idea that Paddington represented other refugees was a definite hook. "I really did key into that. You can't relate to the story otherwise; you can't help but fall in love with him. And if you can't relate to that, there's something wrong."

In other ways, however, Paddington is all fun and fantasy. For a start, its dominant colour is bright red. Mr Brown has turned beige with fatherhood, but their fairytale house is the work of his wife, an illustrator; every room vibrates with colour and ornament, while a tree painted up the stairwell sprouts or drops its blossoms according to the prevailing family mood. Up in the attic where Paddington sleeps, a doll's house opens to show all the rooms in the house in their ornate, rainbow glory. Mr Brown has decreed that his tearaway son should play only with old-fashioned toys for safety's sake, so there is a lot of mucking about with toy trains and Meccano.

"It's not tethered to a particular period as such; it's set in modern day but it's all so beautifully stylised and there is a sort of old-fashioned air to the clothes and colours," says Hawkins. "Everything is heightened."

The city is also heightened, at least to the point where a bear walking down the street isn't too freakish. Bonneville compares Paddington's London to the Paris of Amelie. "I like the idea of London being somewhere you don't quite believe in," the director says.

So the terrace of houses where the Browns live are painted the colours of fruit pastilles and a calypso band keeps popping up next to him, playing the music that accompanied the first wave of West Indian immigrants who arrived on the Windrush in 1948. "London is the place for me!" they sing, echoing a Trinidadian musician who called himself Lord Kitchener and sang his lilting composition to a Pathe newsreel crew when he first got off the ship.

And perhaps it really was, says King. "Without trying to be political about it, big cities can feel like safe places for people who feel a little bit different." Paddington is unquestionably different; he acknowledges that, even as part of the Brown family, he will never be like everyone else. "But that's all right," he decides. "Because I'm a bear."

Paddington opens on December 11. 

Bear Essentials: Five films about ursine friends

1. Ted (2012): Mark Wahlberg's talking teddy, voiced by Seth MacFarlane, is a very bad bear indeed as they both become adult animals. A bromance for furries everywhere.

2. Grizzly Man (2005): Director Werner Herzog finds transcendence in the lives and deaths of two environmental activists who lived among Alaskan grizzly bears.

3. The Bear (1988): An orphaned cub is protected from hunters by an adult male black bear in Jean-Jacques Annaud's ultimate animal tear-jerker.

4. The Edge (1997): A billionaire with trophy wife (Anthony Hopkins) and the wife's lover (Alec Baldwin) are stranded in the Alaskan wilderness, where they are pursued by a large, lumbering and unfortunately very appealing Kodiak bear. Notable for the way Alec Baldwin is obliged by the script to yelp "That bear is reading my mind!" without laughing.

5. Winnie-the-Pooh (1966 onwards): Disney travesty of A.A. Milne's cherished stories of a child's imaginary woodland world peopled by his toys come to life.

And two advertisements:

1. The 1993 computer animation for Coca-Cola showing polar bears (who have been major players in Coke ads since 1922) as if at the drive-in, gasping in awe at the Aurora borealis.

2. More fun was the 1994 TV commercial for Bundaberg rum, with a bunch of polar bears in the pub ordering fish suppers and getting furrily friendly with the girls as the Bundy flows. Says one old bloke in the corner to his mate:  "Those bears know how to have a good time!" They do indeed. Cue the jingle: "Bears have a good time…"