Three days later I found myself standing on top of a termite hill staring at another termite hill through binoculars.

I knew that what I was standing on was a termite hill, but was disappointed that the thing I was staring at was not a northern white rhinoceros, since we had been walking determinedly towards it for upwards of an hour in the blazing midday sun in the middle of what can only be described as Africa.

Also we had run out of water. I could scarcely believe, having been brought up on a rich diet of H. Rider Haggard, Noel Coward and the Eagle, that the first thing I would do on encountering the actual real savannah plains of Africa would be to march straight out into them in the midday sun and run out of water.

Though I wouldn't admit it, of course, having been brought up on a rich diet of H. Rider Haggard, etc., I was actually a bit frightened. The point about not running out of water in the middle of the savannah is that you do actually need the stuff. Your body regularly mentions to you that you need it, and after a while becomes quite strident on the subject. Furthermore we were miles from anywhere, and though there were a number of theories flying around about where we'd left the Landrover, none of them so far had stood up to rigorous testing.

I don't know how worried Mark or Chris were at this point, because it was difficult to get them - particularly Chris - to say anything coherent. Chris is from Glasgow, and is an excellent specimen of one of the northern races: fair-haired and fair-skinned, never happier than when carrying a DAT recorder and a microphone wrapped up in something that looks like a large dead rabbit across the Scottish moors with the wind and rain lashing at his gritted teeth. He is not a natural for the savannah. He was walking by now in smaller and smaller circles and discussing less and less sensible things while glowing like a traffic light. Mark was getting red and sullen.

The two women with us thought we were complete wimps. They were Kes Hillman-Smith, a rhino expert, and Annette Lanjouw, a chimpanzee expert.

Kes Hillman-Smith took over from me on the termite hill and scanned the horizon. Kes is in fact one of the world's leading experts on northern white rhinos, but she was not a world authority on where in a national park the size of Scotland, the twenty-two surviving white rhino were to be found at that precise moment.

I may have got my facts wrong. I seem to have conflicting information on the size of Garamba National Park. One opinion is that it is only 5,000 square kilometres, in which case I would have to say that it was only the size of part of Scotland, but it was a big enough part for twenty-two rhinoceroses to be very effectively hidden in.

Kes had been very sceptical about the termite hill from the outset, as it would befit a world expert on rhinoceroses to be, but since it had been the only thing in the distant heat haze that looked even remotely like a rhino, and we had come all this way, she had suggested that we might as well go for it.

Kes is a formidable woman, who looks as if she has just walked off the screen of a slightly naughty adventure movie: lean, fit, strikingly beautiful, and usually dressed in old combat gear that's had a number of its buttons shot off. She decided it was time to be businesslike about the map, which was a fairly rough representation of a fairly rough landscape. She worked out once and for all where the Landrover had to be, and worked it out with such ruthless determination that the Landrover would hardly dare not to be there, and eventually, of course, after miles of trekking, it was exactly there, hiding behind a bush with a thermos of tea wedged behind the seat.

Once we had revived ourselves with the sort of mug of tea which makes the desert bloom and angels sing, we rattled and rolled our way back to our base, which was a small visitors' village of huts on the edge of Garamba National Park, separated from it by a small river. We were currently the only visitors to the park which, as I say, is the size of part of Scotland. This is quite surprising because the park is one of Africa's richest. It is situated in north-east Zaire, on the border with Sudan, and takes its name from the Garamba river which meanders from east to west through the park. Its habitat is a combination of savannah, gallery forest and papyrus marshes and contains currently 53,000 buffalo, 5,000 elephants, 3,000 hippos, 175 Congo giraffes, 270 species of birds, 60 odd lion and some giant eland, which are large, spiral-horned antelopes. They know there are giant eland in the park because we saw one. The last time anybody saw one there was in the nineteen-fifties. We were rather pleased about that.

The park is very scantily visited, partly, I imagine, because of the insane bureaucratic nightmares which assail any visitor to Zaire, but also because the park is three days' overland journey from Bunia, the nearest airport, so only the most determined visitors actually make it.

We were lucky. The Senior Management Adviser on the Garamba Rehabilitation Project, Charles Mackie, came to pick us up from Bunia in an anti-poaching patrol Cessna 185. The runway on which we landed just outside the boundaries of the park was merely a flattened piece of grass along which we bounded and hopped before finally slewing to halt. It was a dramatic change from the cold mistiness of the Virunga volcanoes - grassland as far as the horizon in every direction, hot, dry air, a Landrover bounding along dusty roads through the savannah, and elephants heaving themselves along in the hazy distance.

That evening we went to have a meal at the house which Kes shares with her husband Fraser, a park conservation manager. It was a house they built themselves, out in the bush on the edge of the river. The house is a long, low, rambling structure, full of books, and largely open to the weather - when it rains they lower tarpaulins over the spaces where the windows aren't. For the two years it took them to build the house they lived in a tiny mud but with a pet mongoose that used to dig up the floor looking for worms, a dog, two cats - and a baby.

Because their house is so open, it is regularly full of animals. A young hippo, for instance, frequently comes to chew on the pot plants in their living room. It often spends the night asleep in their bedroom with its head resting next to the (second) baby's cot. There are snakes and elephants in the garden, rats which eat all their soap, and termites gradually nibbling away at the support poles of the house.

The only animals that really worry them are the crocodiles, which live in the river at the bottom of the garden. Their dog was eaten by one.

'it is a bit of a worry,' Kes told us. 'But we just have to make our lives as comfortable as possible under the circumstances. If we lived in the city we'd be just as concerned about the children getting run over by a bus or abducted as we are about them being attacked by a crocodile.'

After dinner they said that if we wanted to stand a hope in hell of actually seeing any rhino then it would help considerably if we could find out where they actually were. They suggested that we ask Charles to take us up in the Cessna the next day, and then perhaps we could go out by Landrover again the day after that and see how close we could get to them. They contacted Charles over their battered old field radio, and made the arrangements.

Charles flies his plane the same way my mother drives her car round the country lanes in Dorset. If you didn't know she had done it invincibly every day of her life for years you would be hiding in the footwell gibbering with fear instead of just smiling glassily and humming `Abide With Me'.

Charles is a thin and slightly intense man, and also rather shy. Sometimes you think you must have done something which has mightily offended him, and then realise that the sudden silence is only because he can't think of anything to say next and has given up. In the plane, though, there is so much to see that he is very talkative and also, of course, very hard to hear.