The first time I met Oliver I knew two things immediately and with absolute certainty. The first was that this little yellow Opel Kadett was the car in which I would drive across Botswana. And the second, that his name was, indeed, Oliver.

We were in the process of researching and setting up yet another overambitious Top Gear feature in which the three of us would attempt to drive across what Jeremy [Clarkson] dubbed, rather romantically, “the spine of Africa”: Botswana. We were trying to prove to the people of Surrey that just because you’ve moved out from London and there is, from time to time, a leaf on the road outside your suburban house, you don’t really need a massive 4x4 with the off-road capability of a lunar buggy and the engine power of a naval frigate to cope with transporting your kids two miles to school.

We were, therefore, going to attempt this 600-mile journey in two-wheel-drive cars. We could make our selection only from cars bought in or near Botswana. James [May] had bought a huge Mercedes on the grounds that that was what people used out there, given the chance, and in the unlikely event that it broke down it could be fixed by engineers familiar with the car, drawing on a readily available stock of parts. And he was probably right. Jeremy had bought a Lancia Beta. Because he is, sometimes, bonkers. I arrived in Oliver and the other two laughed. A lot.

THE Makgadikgadi Pan salt flats are a thin crust of dried-out salt that covers what local myth avows is a bottomless pit of ooze and slime. In fact the whole area is an ancient dried-up sea. As the water was boiled off by the African sun over the millennia, it released its salt to lie in dazzling white plains on the surface. Underneath it there lay, and still lies, the original sea bottom. An eternity of fish, algae and plant life rotting quietly into a primeval ooze probably not unlike the one from which our distant ancestors crawled.

We had not made an especially impressive arrival at the salt flats.

At least, not when compared with the one made by the vice-president of Botswana. As we stamped around in our new boots, he and his entourage landed next to us in microlights.

They were very polite and welcoming for a bunch of people who travel like James Bond villains. We told them what we were going to do. The vice-president laughed and said something to the effect that we would almost certainly die.

What we were about to attempt had never, as it turned out, been done before. We were the first. I’m not sure that the vice-president understood entirely why we were going to try to drive across the lifeless, drought-ridden, death-stalked plains of his sunbaked salt flats in cars more suited to tootling around the back streets of Eastbourne in search of a loaf of bread and a newspaper, but he managed at least to wish us well.

TO stand a better chance of making it we had to lighten our vehicles.

James’s Mercedes, weighing in at a couple of hundred or so tons, had to shed some weight to drive on tarmac, let alone cross a 3in crust of prehistoric salt. So he cut off the doors, the boot lid and the bonnet, threw out the back seat, most of the windows, the bumpers and the spare wheel.

Jeremy performed similar surgery on his Lancia with the help of his favourite tool, in fact the only tool I’ve ever seen him wield — a hammer.

I stood next to Oliver with a screwdriver and a hacksaw, listening to the assorted crunches, bangs and grindings as the other two worked on lightening their cars. And I couldn’t do it. He had survived out here in Africa for more than four decades and I was not about to be the straw that broke this tough old camel’s back.

My only complaint was the vinyl seats: who the bloody hell decided that the best material with which to cover the seats in a car bound to spend its life under the baking African sun was vinyl? It heats up until it’s hotter than that same African sun and then, when you sit on it, assuming you’re wearing shorts — which you will be — there’s a smell like a barbecue and the flesh on the back of your legs and arse is welded to the seat. When you stand up again, you leave a human hide seat cover in the shape of your arse stuck to the seat. Why? Why vinyl? Why not velour, canvas, paper?

Despite this we made it across the flats. I knew we would. And we made it into the Okavango Delta. But Oliver started to feel the strain.

And then I drove him into a river. I had been trying to find a better river crossing route than the one proposed by James and Jeremy. We weren’t messing about, it was a river we had to cross, to continue on our way through the Okavango Delta. But the point at which they had chosen to make the crossing was, quite clearly, crap.

I have been a keen off-roader for many years and I felt that this had prepared me rather better for challenges such as this one than a life spent mincing around in wine bars quaffing something crisp and white and moaning about taxis. So I went my own way.

I was damned if I was going to risk ruining Oliver in crossing at a point where it was clear to anyone with an ounce of off-roading knowledge that he would sink and be drowned. They made it across but as I drove the muddy margins of the river, I didn’t know this.

Finally, after trawling the banks in search of that special spot, that sweet place where the slope of the bank is just right on both sides and the water itself, through subtle gradations of colour and surface ripples, betrays itself to be shallow and steady, I found it. And I even found a path. It ran down to the river, tyre marks were clear in the shallow layer of mud. So it had already been used. I looked across the broad expanse of brown water and there, emerging from the other side, was my exit path. This, then, was perfect. I drove in the tried and tested manner of off-roaders crossing rivers: enough power to make decent headway and enough speed to push a tiny bow wave ahead of the wheels if it grew a bit deeper in the middle. Which it did. A lot deeper. Then the path sort of stopped and turned into a shelf. Which we dropped off. And I experienced the novel, though terrifying, sensation of setting sail across a river in the middle of the Okavango Delta in a shopping car called Oliver.

His front wheels gave up their grip with a gentle bob and he settled down onto the surface of the water as his rear wheels gave a final little push to the edge of the shelf. We were floating. And then we were sinking.

Water gushed in through Oliver’s dashboard, quickly filling the cabin until it came over my knees and began its slow, cold climb up my stomach. I loved Oliver. I knew that. But I didn’t fancy dying with him that day. I pushed the door open and hurled myself out into the water. My feet never brushed the bottom.

With his load lightened, Oliver floated serenely alongside me and we swam together for a while as my head whirled with the horror of what I had done. The film crew were to hand, of course. But they were temporarily incapacitated by an outbreak of hysteria while I swam alongside my yellow Opel Kadett. With the hollow feeling known only to those forced to abandon a friend at sea, I swam back to the bank and clambered up the muddy shoreline. I stood and dripped, my mouth half open.

We did get him out. Of course we did. I slid back into the water, kicked out and reached Oliver to tie the rope around his bumper where he bobbed, nose down. The door was still open. I climbed into the cabin and lowered myself chin deep in the water to sit in the driver’s seat as we hauled him out.

Back on the bank, when I opened the door again a rush of river water flowed out on to the ground and it symbolised, for me, the rush of guilt that flowed after me as I climbed out and stood next to Oliver’s stricken form. Having drained, dried and cleaned everything I vowed to ship Oliver home to the UK. He’d got me this far, I wasn’t going to walk away and abandon him.

Eventually we made it. All three cars and their drivers drew up at the border between Botswana and Namibia, dusty, battered and dented, having driven 600 miles across some of the roughest terrain Africa could throw at us. We had no four-wheel drive and no firebreathing engines. We had proved our point about school-run 4x4s.

And, yes, I took Oliver home. He’s here now.

© Richard Hammond 2008

Extracted from As You Do, published by Weidenfeld & Nicolson at £18.99. Copies can be ordered for £17.09, including postage, from The Sunday Times BookFirst on 0870 165 8585