Gesturing at the 16 tons of truck and grit that he's navigating down a steep snow-covered Buckinghamshire hill, Paul Nairey says: "These things aren't invincible you know." Moments later, as if to prove his point, the enormous vehicle lurches and begins to slide along the ice. "See what I mean?" "Mmm," I agree, digging my feet into an imaginary brake pedal.
With its steep hills and precipitous winding roads, High Wycombe and its surrounding area is already a gritter's nightmare. But the past few weeks have tested even the most seasoned road maintenance men. And 47-year-old Paul – who has worked in the same depot for 18 years – certainly qualifies as one of those.
"People assume that, being in a gritter, you must be invincible. But it's just the same as any other lorry," he says. "Not all of them even have four-wheel drive and when we take them down the hills it can be terrifying – sometimes you slide so much that you go down backwards and I've even had the whole back of the lorry overtake the front. We don't even get training for driving them in these conditions."
Leaving the High Wycombe depot and driving towards the Oxfordshire border, our route takes in a string of villages and hamlets so picturesque they are constantly used as the backdrop for television series such as The Vicar of Dibley and Goodnight Mister Tom. The idyllic setting suggests a bygone era, but the irate residents say otherwise.
In Lane End, a well-dressed woman climbs into a Mercedes, takes one look at the gritter and lets rip a string of expletives. Not that we can hear them over the roar of the engine, but judging by her angry expression she's not saying "Good day".
"I've become quite good at lip-reading," Paul says, avoiding her gaze. "We get a lot of abuse. I've had everything from sarcastic hand clapping to people screaming and sticking their fingers up or just not moving their cars. We've had to get used to it, but it does annoy me. We're the ones making sacrifices while everyone else gets drunk at Christmas and New Year."
But the gritters are only likely to get more unpopular. Like many other places in Britain, High Wycombe was still recovering from a pre-Christmas dump of snow when it received an even bigger icing of the stuff. The "salt" that Paul and thousands of other drivers have been pouring on to the country's roads is now running out.
Nothing like the pure white table variety, this road salt resembles fine brown gravel and comes direct from one of Britain's three underground salt mines. In Buckinghamshire, the grit comes from Winsford Rock Salt Mine in Cheshire. Or at least it would, but for one problem: it's not coming. "From what we're told there's no reserves left there," explains Eric Meek, manager of Buckinghamshire's road maintenance. "We ordered it ages ago, but it's coming straight out the mines to wherever has the most need and we don't know when it will come to us."
The Government's Salt Cell – the cold-weather equivalent of Cobra that appears when grit becomes a national concern – has finally rumbled into action this week to ration salt and distribute it to the councils and highway agencies they deem to be in most need. Like councils across the country, Buckinghamshire has to send daily figures detailing the levels of grit it has remaining. But you don't need hi-tech digital weighing gear to see that their stocks are low. The depot's snow-topped salt barn is beginning to resemble a massive and ominously empty igloo. Dwarfed in a corner beneath the cathedral-high ceiling is a pitifully small heap of grit.
The council has now been forced to cut the road gritting routes from seven down to four – just to make sure stocks will last long enough to keep the roads running that might be needed in an emergency. As well as this, they are gritting on the second-lowest setting, distributing just 10 grams per square metre, instead of the 40 grams they would normally use in such adverse conditions.
At the snow-covered depot outside High Wycombe, a group of men with high-visibility jackets stretched over a multitude of layers are waiting to fill their trucks with salt. "Just what we need, more snow," groans 33-year-old John Harte, as fresh flakes fall around the lorry that he is preparing to refill the county's salt bins.
Back in the gritter, Paul is trying to demist the foggy windscreen. "Make yourself at home," he says, as we wait our turn to fill the truck. The temperature gauge reads minus 7C and the smallest breath leaves a cloud hanging in the air. Home is not the first place that springs to mind. But for Paul, that is exactly what this draughty lorry has begun to feel like over the past few weeks.
"I got married in July and I was looking forward to a first Christmas with my wife, but she's hardly seen me," he says. "The only day I got off was Boxing Day. When I tried to go out to do my Christmas shopping on Christmas Eve I got called back to the depot."
But few will notice the efforts he and the other road workers have made. The local paper has already started a pothole campaign. "Once the snow melts we'll be flat out filling in potholes – they happen every year when the ground freezes over like this. But people don't realise it's the same people out gritting that need to be free to mend them. We do take a knock – people expect everything to happen by magic."