It is not clear where mainstream civilisation has petered out. Perhaps on the suburban outskirts of Winnipeg, the capital of Manitoba, which keeps itself away from the worst of the winter just 65 miles above the American border. Maybe somewhere near The Pas, a town roughly midway up the torso of what is Canada’s sixth biggest province; a lonely pinprick of light on the aerial map as I fly north.

By the time I touch down in Churchill, man’s domination of the environment has been all but prised away, finger by freezing finger. In its place are endless swathes of sparse rocky tundra and the cold grey waves of Hudson Bay.

The polar bear. That enigma of the Arctic. A mammal of pristine white fur which will turn its coat blood-red in the guts of a seal. An assassin imbued with terrifying brute power, but also grace and magnificence. A traveller that lollops through the popular consciousness, yet inhabits only a far-flung portion of the planet.

"Churchill calls itself “The Polar Bear Capital of the World” – a reasonable boast" Credit: alamy

An animal so cute and winsome that it populates children’s cartoons and the cuddly-creature sections of toy shops, yet a killer so awfully efficient that just 10 seconds in its paws will cost you your life. This latter point is the reason why, almost as soon as I meet him, Patrick Rousseau is talking to me sternly.

“If I say 'get on the bus’, you get on the bus,” he says, his voice a mouthful of gravel. “A male polar bear could hide in that bush over there,” he continues, indicating a patch of scrub that is neither large nor snow-clad, “and you will not see it. Do not look around for the problem. Because the problem can come at you very fast indeed.”

He knows his subject. A 67-year-old former national park ranger and semi-retired wildlife biologist, he has spent most of his career above the Arctic Circle, mainly on Baffin Island, the giant outer chunk of Canada’s Nunavut territory. Over the next four days, he will be not so much my guide as my guardian, an expert to listen to at all junctures.

“It is a harsh world up here,” he says, reinforcing his message. “It is not a Walt Disney world.”

Downtown Churchill Credit: alamy

The bus he drives is a classic North American school coach, painted that inimitable shade of custard-yellow. It looks rather incongruous as it trundles into Churchill, a town of slate greys and muddy blues which puts its shoulder to the wind as Canada’s only deep-water port in the north.

Although not remote in terms of raw latitude – at 58°N, it sits no higher up the planet than John O’Groats (and thus, strictly, is sub-Arctic) – it is an outpost removed from the rest of its own country. It clings to the western side of Hudson Bay, so divorced from its provincial capital (Winnipeg lies some 625 miles to the south) that no roads reach it.

Arctic fox Credit: alamy

The only way to arrive, other than by plane, is on the Winnipeg-Churchill rail line, which crosses Manitoba via 1,054 meandering miles. The journey takes 36 hours.

Those who make the trek enter the realm of the Arctic’s big beast. Churchill calls itself “The Polar Bear Capital of the World” – a reasonable boast due to its location, on a shelf of land which juts out into the bay. This makes for a barrier which catches melting pack ice as it drifts south in summer, bringing with it a cargo of bears that, come June and July, will disembark on the beach to snooze out the hot months, dreaming of autumn and the re-congealing sea – when the essential business of hunting for seals will begin again.

This explains why, in October and November, as Hudson Bay starts to solidify and bears pace on the shingle, anxious to leave, Churchill is full of tourists.

Heed the warning signs in Churchill Credit: alamy

Canada can claim about 17,000 of the globe’s estimated 25,000 polar bears, and some 500 of them roam within range of town. It also explains some of the obvious precautions – not least the high metal fence that surrounds the school.

On the beach which ebbs behind, a sign re-emphasises that this is scarcely a site for sunbathing. “Stop. Don’t Walk In This Area. Report Bear Sightings,” it shouts. Bears have been known to doze among the rocks, a nasty shock for the careless.

For all this, the town is not, mercifully, the ideal place to spot these photogenic predators. That is Cape Churchill, a sandbar 35 miles east. And so I find myself in a helicopter, the busy blades eating up the distance.

At this elevation, the unremittingly spartan nature of the landscape is apparent – the tundra barren and almost treeless, the lakes that pockmark its surface already surrendered to winter’s touch.

"Canada can claim about 17,000 of the globe’s estimated 25,000 polar bears, and some 500 of them roam within range of Churchill" Credit: alamy

Easy to see, too, are the bears – eight of them strung out along the spit, creamy haunches and giant heads smeared with the mud of these tidal flats, but still discernible against the brown seaweed. Glimpsing them like this, off-duty and at leisure, is a thrill that no YouTube showreel could ever replicate.

The urge is to be closer. This is possible via heavy mechanics – specialist “tundra buggies” which can rumble across the unforgiving ground in search of their quarry. Of course, “buggy” is a ridiculous misnomer for a machine that comes equipped with six colossal wheels – each nearly 7ft tall to keep the chassis away from the Manitoba dirt and any aggressive outbreaks of ursine curiosity.

Staring at the fat, reinforced tyres which support the vehicles, I find myself wondering about the impact of their treads on the soil beneath – only to be assured that the way ahead is paved. The area was, perhaps unsurprisingly, a hive of Cold War activity.

What is now the airport was once Fort Churchill – an American-Canadian airbase which kept two suspicious eyes on the Soviet Union in the Sixties and Seventies. The main legacies are a military-length runway (9,200ft; long enough for a Boeing 747), and a warren of “roads” fanning out to Cape Churchill – once a venue for tank drills, now a playground for guided buggy jaunts.

And so we roll, out towards the seafront, and into nothing. Nothing at all. For three hours, there is not even a hint of a bear. An Arctic hare skips by, unfazed by the morning. Rousseau is puzzled. “A washed-up whale carcass?” he suggests, pondering whether an unanticipated food source has lured the bears to an unseen section of the coast. And so we sit, scanning the setting – the weak sun slanting across the tundra, turning it a lunar-silver.

Then he appears. A lone adult male. He lumbers towards us without urgency or fear, a king in his throne room, a champion with no challengers. He spots the buggy, halts, then continues, sniffs the tyres, puts his feet on the front, lifts himself upright, tries to peer in.

Unflustered, he wanders on – tailed, 50 yards behind, by a young mother with two cubs. She comes cautiously, her charges – both under one – following dutifully. She is seeking the relative safety of the near-interior, her offspring desperately vulnerable to a male who has not eaten for four months.

He is up the trail, and she knows it – but he is aware of her too, nervous of her maternal protectiveness when his strength is low. So they do a dance of sorts – she keeping her distance, he holding his poise and his pride, until she has faded from view. As she disappears, I realise that nobody on the buggy has spoken for minutes.

“They have a tough life,” Rousseau says. “Successful males only live to 20, females to 25. Sixty per cent of cubs die before they are three. This is nothing to do with man. If wolves don’t get them when they emerge from the den, there is a good chance an adult male will. They are a cannibalistic species. They need to be to survive. That’s the reality.”

This is an unnerving thought, but one which brings an extra frisson to what awaits when the buggy returns to the depot. Another bear has stomped through only 20 minutes earlier, startling one of the crew (and his thankfully alert dog), implanting tracks in the snow. I put my boot next to one of these enormous prints. The size of the claws makes me shiver.

After this, Churchill feels like a metropolis, a safest of havens. What, on first appraisal, seemed a featureless slab of upcountry pragmatism reveals itself as a web of humanity, its 800 residents milling around a compact grid of doughty welcome.

"In October and November, the ice of Hudson Bay starts to solidify and bears pace on the shingle, anxious to leave" Credit: alamy

There is the little post office with its polar-bear postcards, the liquor store with its clusters of wine and vodka bottles, the Itsanitaq Museum dissecting the Inuit culture of the region via carved-wood kayaks and whalebone sculptures.

Then there is Gypsy’s, a restaurant where the whole community – tourists, guides, locals – unites around a delicatessen counter that would not disgrace a hip Brooklyn street. There are soft cheeses and sliced meats, shrimp risottos and bowls of thick clam chowder, banana muffins, cheeseburgers, hanger steaks.

The Gypsy's restaurant in Churchill Credit: Alamy

And mutterings of concern. Out in the darkness, the port, which has been in operation since 1932, is locked in limbo – mired in a red-tape dispute between the American company which owns it and the Canadian government – with its immediate future is uncertain.

Not so much lethal threat as crucial lifeblood, the polar bear might well be the most reliable presence in this town on the edge of the world.

Essentials

Getting there

Air Canada flies to Winnipeg from Heathrow via Toronto and Calm Air links Winnipeg to Churchill. Despite the recent closure of the rail line to Churchill from Gillam, travellers can access the nearby city of Thompson by rail and fly to Churchill via Calm Air from there. The best times of the year to visit to see polar bears is October and November.

Touring there

Natural Habitat Adventures offers a Classic Polar Bear Adventure expedition in Churchill – six-day tours from US$6,695 (£4,793) per person based on two sharing, including return flights from Winnipeg, a dog sledding excursion, cold weather gear including a parka and boots during your trip, all activities and entrance fees, evening wildlife and cultural presentations, taxes and service charges.

More information

travelmanitoba.com; tourismwinnipeg.com; canada.travel