YOU don’t have to be top sleuth in the No.1 Ladies’ Detective Agency to appreciate that there’s little fertile land in Botswana.

A cursory glance out of an aircraft window is enough for that.

Much of this giant southern African nation is an enormous sandpit, part of the Kalahari Desert, into which the lion’s share of its seasonal rainfall simply seeps away.

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Yet this is the nation which contains the world’s largest inland river delta, the Okavango, which supports one of the highest concentrations of wildlife in Africa.

Solving the riddle of where the Okavango comes from and where it goes is a task you might set Precious Ramotswe, the main (and only) detective in the aforementioned Botswanan agency, created by author Alexander McCall Smith.

But I’ve got my own walking lexicon of all things African to hand, called Gareth, and it is he who explains how this wetland, about the size of Wales, is fed by a river which starts in the mountains of Angola, two countries away to the north.

In Botswana, it hits the buffers and comes to a grinding halt among all that sand, where it slowly evaporates; not before it has brought life to everything, from the top predators to the tiniest termites.

I know this because many of them seem to be gathering outside my tent.

It’s night and the hippos are bellyaching, lions are sounding off in the distance and a hyena is snuffling around the canvas.

Fortunately, I also know that somewhere out there is Gareth the guide and if I holler loud enough, he’ll come running with his gun.

Believe it or not I am on a Saga trip, which involves lots of lovely cups of tea. Tea and porridge at 5am, when we first get up for
the morning game drive.

Then tea and biscuits around 9am, when we take a break by the side of a marsh or the foot of an escarpment, sated with wildlife sightings.

Then again after lunch, conjured up over an open fire and eaten at a table immaculately set, perhaps in the shade of a rain tree. Again in the afternoon, often with home-made sponge cake before the last game drive of the day.

And, finally, after a three-course dinner by lantern light, surrounded by our ring of tents.

This isn’t a sedentary Saga trip.

We are on a mobile camping safari, an adventurous African journey that brings you face to face with nature, red in tooth and claw.

Mobile safaris are usually operated by two teams: the back-up staff who go on ahead and set up camp, get the home fires burning and prepare the meals; and the game drive vehicle with the guide and his passengers, which takes a more circuitous route between camps.

The staff make the camps feel remarkably cosy. A wide ring of tents surrounds the main communal gazebo under which the dining table is laid, with napkins and proper tableware.

At the opening to the camp is the fire, with comfortable canvas chairs for after-dinner philosophising and star-gazing.

The “mobile” element means that every other day we move on, travelling rarely more than 100 miles.

However, progress is slow on sandy, rutted tracks and without sharp-eyed Gareth pointing things out and providing us with tea, it would have been hard work.

This form of safari makes everything more accessible, avoiding the expense of flying and using luxury lodges.

As for the wildlife, we have access to that, and it to us, 24 hours a day.

We start in the Moremi Game Reserve, around 2,000 square miles, where we can see the devastation too many elephants can wreak on mopane forest.

As we patrol the banks of the River Khwai, we see a lion, herds of graceful impala and some curious giraffe.

Then, heading north, we come across a pack of dogs, with puppies lying in a heap, sleeping in the sun.

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African wild dogs are the second-most threatened species in the continent.

We count ourselves lucky to have seen them.

Yet it is the Savuti Marsh, in the Chobe National Park, where we really see it all.

It’s a massive area of waterlogged grassland, striped with pelicans and with herds of buffalo like stationary freight trains in the distance.

Here, Gareth peers over fresh paw prints, striding out into the marsh to check its depth before driving the Land Cruiser through.

He finds us snoozing lions, aggressive elephants, swooping eagles and a lazy leopard, dappled in sun and stretched out on a lower branch of an acacia tree.

These may sound like timeless scenes but they’re only a recent development in this part of the Okavango.

The marsh, says Gareth, almost dried up a couple of years ago but then the tectonic plates shifted under the ground and water spilled back in again.

So in camp that night I have the perfect excuse for my tremor when the lions roar; it wasn’t me, it was the earth that moved.

FACT BOX

Saga (0800 414 383/www.saga.co.uk/africa) offers an 11-night Botswana and the Jewel of the Kalahari tour from £2,799pp (two sharing), full board.

Price includes camping in the Okavango Delta and Chobe National Park, return flights from Heathrow to Livingstone, game drives and excursions.

Departs May 4, 2012. Botswana Tourism: 0207 499 0031/www.botswanatourism.co.bw