Sarah Shuckburgh enjoyed the proximity of danger on a Botswana bush walk - until she discovered a small rodent in her tent.

I can feel the lion's eyes on me. With every twitch of the waist-high grass, every scuffle, every snapped twig, I think my last moment has come. If only I were safely at home, with a good book. Instead, I am hiking through the African bush, and, yards from me, a hungry lion is lurking, ready to pounce and kill.

I try to keep close to Gary, our guide, as he strides along, rifle loaded and ready to fire. At least he looks the part - narrow-eyed and lantern-jawed, in safari hat and khaki shorts.

"Have you ever had to use that gun?" I whisper, nervously.

"Yes," grunts Gary.

I'm not sure whether this is good news or not. Behind us, Indian file, come my three companions, eerily subdued. Even Caroline, an old bush hand, is struck dumb with fright. Bringing up the rear is Oti, the taciturn African tracker, eyes swivelling left and right.

We are on a three-day trek in northern Botswana, and until now everything has been wonderfully exhilarating. On the first morning, we got our instructions: walk in single file, avoid sudden movements or loud noises, and above all, obey these hand signals - stop, lie down, climb a tree, hide, run. The dangers are thrilling - we must inspect our boots for scorpions, and wear stiff gaiters to ward off stinging grass-seeds that twist their way through socks and burrow into flesh.

"Don't worry about snakes. They'll hear you coming if you're wearing heavy boots," says Gary.

Everything we pass is fascinating to my inexperienced eyes - a sloughed snakeskin; heaps of half-digested elephant dung; a bleached hippo skeleton; 10ft termite mounds, hard as concrete, with jackal-berry trees sprouting from their summits. A strangler fig, grown in a crevice from a seed dropped by a bird, coils round the host tree, killing it. Two bat-eared foxes frolic by their den; a spindly-legged giraffe bends over her knock-kneed baby; warthogs trot comically with tails aloft; and we surprise a painted dog as it basks elegantly in the sunshine. Vultures wheel overhead. A bull elephant plods across the shimmering savanna towards a herd of impala and wildebeest. Gary points out fresh leopard tracks, and we learn an A-Z of droppings - aardvark, cheetah, jackal, kudu, ostrich, porcupine, zebra.

As we nibble muesli bars in the shade of a candle-pod thorn tree, Oti weaves us bracelets from stripped and twisted bark, and creates foaming lather from crushed sprigs of soap plant. Gary eyes a distant herd of buffalo. To me they look as innocuous as farmyard cattle.

"We don't want them to come any closer," he mutters. "Nobody survives a buffalo charge."

"He's only saying that to alarm us," whispers Caroline, hopefully.

The routine of our days does not vary. We are woken before dawn with cups of tea and rock-hard rusks. By torchlight, shivering and cursing, we grope our way into our warmest clothes, and try in vain to brush our dust-caked, tangled hair. After a breakfast of muffins and fruit, eaten huddled round the embers of the bonfire, we sally forth as the first rays of sun light up a thousand tiny clouds. Our walk takes us along dry riverbeds, across parched grassland, and into scrubby woods, pollarded by elephants.

Stripping off jerseys and donning sunhats as the sun climbs to its zenith, we hike for four or five hours before reaching our next camp, where lunch is laid out under an awning. Retiring to our tents, we snooze through the blistering midday heat, emerging for tea (banana bread and iced buns) and another walk for two hours until sunset.

We sip sundowners as baboons screech overhead, pixie-faced babies clinging to their parents' bellies. African skies are as huge as I'd been promised and sunsets are breathtaking - a lurid blaze of red, orange and purple, with inky silhouettes of solitary trees; and then sudden darkness. Under a million stars, we venture, one by one, to the bush shower - a wonderful outdoor contraption in which water, heated on the bonfire, sprinkles from a dangling bucket. Something has nibbled the soap, and there are alarming rustles in the darkness. Visiting the loo is also an adventure - the open-air long-drop harbours unimaginable creatures, all waiting to bite or sting.

Wrapped up against the winter chill, we have supper beside the glowing fire. Cats' eyes glint in the lantern-light, as nocturnal hunters pass. Loping hyenas loiter in the scrub, attracted by cooking smells.

Later, clutching hot-water bottles, Caroline and I lie awake, the bush cacophony filling our tent with unidentifiable chirps, squeaks, croaks, howls, wails, and roars. The nights are wild and windy, the canvas shudders, and heavy pods and twigs plop alarmingly on to our flimsy roof.

I have never been anywhere nearly as remote as this - six hours' drive from the nearest village; a hundred yards even from our companions. The front of our tent is made of netting, and shafts of moonlight allow a monochrome glimpse of the terrors outside. In whispers, we swap scary stories. Did you read about the boy who was photographing game at night, fell asleep with his tent-flap open, and was eaten by hyenas? How about the girl who was dragged from her tent by a lioness? Didn't Gary say that baboons can unzip tents? An elephant could easily flatten our camp. Hippos swallow people in one gulp.

Suddenly Caroline shrieks and leaps out of bed, flapping her arms. Completely frantic, I fling back my bedclothes and grope wildly for my torch. As I switch it on, an armoured cricket tumbles from Caroline's nightie, and I catch sight of a small mouse scuttling across the matting.

Now it is my turn to scream. Caroline heroically dons her Davy lamp and, stumbling over rucksacks and boots, eventually frightens the mouse towards a crack in the netting. Back in our campbeds, we giggle and shiver, and at last the sounds of the bush to lull us to sleep.

The next morning, we are woken by deafening shouts and bangs. The buffalo have wandered into our camp. We sit tight while Gary and Oti fire shots and beat drums to shoo them away. When Gary gives the all-clear, we emerge feeling proud that we survived a buffalo charge, and with a spring in our step, we stride out on the last leg of our journey.

As we munch our morning snack under a palm tree, Gary receives a radio message from a guide in a Land Rover. Five lionesses and their cubs are in woodland ahead of us.

"Best to avoid the trees, and keep in the open slipway," says Gary. We readily agree. But an hour later the radio crackles again. Gary looks worried: "Papa Lima? OK, will do."

"What's Papa Lima?" we wonder. "Panthera leo," mumbles Gary, picking up his rifle. "Lion," he adds. "There's a lone male ahead of us, and he's hunting. We've got to get out of his way."

"This is just staged, to make it more exciting," says Caroline, nervously. But nobody believes her.

Gary keeps pausing, and we stand stock still and silent in our line behind him. The ominously named lion-grass waves and shimmers at elbow height all around us. Every now and then a francolin makes a sudden alarm call, signalling a predator. At other times the bush is eerily quiet. I can picture the lion poised, yards from us, waiting to spring. Which was the hand signal for Stop, and which was Run? My heart is beating like a tom-tom. I think of home, my children, my funeral. How could I have made this daft decision, to come on a trek and risk everything? I try to focus on my boots.

Gradually my feet reach sandier, stonier ground where the bleached grass is shorter, sparser, less easy to hide in. We trudge on in mute terror, until Gary turns, shades his eyes and points. On a high termite mound, near where we walked minutes before, stands a lion, haughty, majestic, magnificent. For a while, he stares back at us, and then he turns away, slips effortlessly off the mound and is swallowed by the pale grass.

Moments later, we reach Zibalianja camp, and are greeted with cool flannels and glasses of guava juice. A gentle breeze wafts under the thatch as we gaze out at the sunlit savanna, and I decide that no holiday could be more perfect.

First published by the Telegraph
©SarahShuckburgh