Rewind a few days – back to the start of our journey on the Tibbitt to Contwoyto Winter Road and a large sign saying 'Travel at your own risk'. At over 350 miles, this is the longest ice road in the world, rebuilt each January and open to traffic in February and March. It begins 45 miles outside of Yellowknife, the capital of Canada's Northwest Territories, before heading north, passing beyond the tree line and across the Barren Lands towards the Arctic Circle. The Northwest Territories, an area twice the size of Texas, is one of the most remote and lonely regions of North America, where the caribou (300,000) outnumber the people (42,500) by seven to one.

Take a look at a detailed map of the region and you'll see that it's mostly coloured blue, an intricate maze of lakes and rivers that makes building any road here practically impossible – until the winter freeze, that is. Once temperatures have dipped and the ice has reached a minimum of 42 inches in thickness, construction of the ice road begins with a fleet of giant snow ploughs following an expertly surveyed route. It's an incredible feat of engineering, achieved despite wind-chill that can dip to 55ºC below. Close to 90 per cent of the road runs across the vast frozen lakes, with the remainder running over 64 land bridges, or portages. (Incidentally, 'portage' derives from the French porter, 'to carry', and dates from a time when the early trappers had to manhandle their canoes over the land separating the lakes.)

Yet it begs the question: why go to such lengths to build an ice road here? The modern road was built in 1982 to truck supplies to a gold mine at Contwoyto Lake, but since the late 1990s it has become the major supply artery for two giant diamond mines. These are some of the richest diamond reserves in the world, with Rio Tinto's Diavik mine producing eight million carats a year – that's approximately a coffee can full of diamonds per day, worth some £800,000. 'The key to making money from mining is volume,' explains Darrell Bohnet, manager at Diavik's Yellowknife HQ. 'Diavik's average extraction of four carats per metric ton is one of the highest in the world. It's a mammoth, round-the-clock operation, with over 500 workers flown in on shifts, two weeks in and two weeks out, 365 days a year. Without the ice road, this operation just wouldn't be viable, as all heavy equipment, fuel and explosives would have to be brought in by air.'

Over 9,000 truckloads of freight are expected on the ice road for the 2006 season alone – that's a lot of expensive flights, even when the cargo is as valuable as the jewels mined in this remote region. It seems only fitting that a common slang term for diamonds is 'ice'.

But getting from A to B on this ambitious thoroughfare is not always smooth sailing (or smooth skating, as it were) for drivers. As we discover from the alarming movement of the road as truck convoys go by, the rock-hard ice is anything but rock-steady, and our predicament is made worse by the fact that we've waited until mid-March to make the drive. The intention had been to go at a time of year when there
is a decent amount of daylight for photography. Unfortunately, it's dangerously close to the time of year that the thaw is due to begin. It's currently a relatively sultry 8ºC and at this temperature, it's touch and go whether the ice road is going to be open at all.

It's not just us and the billion-pound enterprises of the diamond mines that would suffer if the ice road were to close. Approximately 200 miles up the ice road sits Mackay Lake Lodge, where each summer True North Safaris offers fishing, hunting and various other gritty wilderness experiences. Its brochure shows smiling clients brandishing lake trout the size of dolphins. Gary Jaeb, the boss of this Yellowknife-based outfit, has offered to accompany us on the ice road drive – and good thing, too, as the lodge is the only place to stay around here, and with no services to be found en route, we're relying on Gary for our Range Rover Sport's petrol needs, too.

Fortunately, by the morning of our planned departure, temperatures have fallen sufficiently for us to be given the all-clear to start down the ice road. The opening section across Tibbitt Lake – more slush than ice – doesn't do much for our confidence. 'Just a bit of surface melt,' Gary reassures us over the radio. Conditions improve as we head north, though, and the Range Rover Sport's traction allows us to hastily catch up with Gary's pick-up whenever we've lagged behind to take photos.
It's around lunchtime that he hits us with a bombshell. 'Guys,' he growls, deftly shifting the ubiquitous toothpick from one corner of his moustache-shrouded mouth to the other, 'I'm afraid I left all of the meat for this trip back in the freezer.' Having seen his Yellowknife home, its walls festooned with a menagerie of stuffed trophies – including a particularly peevish-looking wolverine – I'm not really surprised at what comes next… 'We may have to shoot a caribou.' My polite, city-boy suggestion that we simply 'muddle through with what we've got with us' is swiftly drowned out by the click of a rifle being loaded. Meat, I take it, is back on the menu.