Britain is blanketed by the heaviest snowfall in 50 years, and anyone on the road either has four-wheel drive – or wishes they had.

But how much difference does driving all four wheels really make? Is it really useful – or just a gimmick with no value other than to sell gullible country types (and their misguided townie cousins) expensive 4x4s they really don't need?

I've done a fair bit of off-roading over the years, in all sorts of 4x4 from the likes of Land Rover, Jeep, Toyota, Mitsubishi and Hyundai. They've been pitted against off-tarmac terrain ranging from wet grassy fields to mud-plastered ravines and boulder-strewn river beds and in any of those situations, there's no doubt that all-wheel drive is a massive help.

But until now I'd never had the chance to find out how much of a benefit four-wheel drive would be on snow and ice. The great freeze of 2009/10 provided the condition, and since last year I've had a Land Rover Defender in the fleet, so I could find out.

20100107defendersnow-209On the face of it the answer is simple: distribute drive to all the wheels and you augment traction and stability. Your 4x4 will go anywhere.

As ever, it's not quite that simple.

On an unreliable mixture of packed snow, slush and ice the Defender rarely showed even a hint of wheelspin – despite being fitted with mud tyres, which are not ideal for ice and snow. Only deliberate provocation – foot-to-the-floor acceleration in first gear – could cause wheelspin.

But that's not the end of the story. Though the Defender had excellent traction in the snow and the slush, thanks to its four-wheel drive transmission, it still needed considerable care on the frozen lanes of south Shropshire.

20100107defendersnow3-209Icy patches still caused the Defender to lose steering control and even on virgin snow – probably the least troublesome of the slippery surfaces it had to deal with – braking distances were considerably longer than normal. The Land Rover is one of the best all-terrain vehicles ever built, but any 4x4 would react in exactly the same way.

Wheelspin might never be a worry when you have four-wheel drive, but traction isn't the only issue. Steering and braking are just as important – and four-wheel drive can do little to help in either of those departments.

The majority of the vehicles I saw on the roads in my 25-mile round trip today were 4x4s, and when you're battling through the kind of snowfall we've seen in the UK over the past week four-wheel drive certainly helps. The advantages are easy enough to see – but it's just as important to understand the limitations.