Charitable exploits and extreme challenges have always interested me so when I read of a Cycling Safari spanning 400+ kilometers through some of Kenya's most inhospitable terrain, at altitudes touching 9,000 feet above sea level and in temperatures of over 30°...all for charity, it was too good to pass up.

We were in the capable hands of Norwood Ravenswood, the UK-based charity that first started exotic excursions to foreign climes some 10 years ago to allow challenge-junkies to raise funds for them, in tandem with the Downs Syndrome Association. They were to make the week's trip as stress-free as possible, with mechanical, physical and moral support all way, and this was the case during our October ride....

As I trudged out of my Fulham flat on a sunny autumnal afternoon, I felt remarkably unfazed at the prospect of cycling round Kenya. Got the kit, got the jabs, got the passport, got the Lariam - all appeared to be in good shape!

At Heathrow, Gordon Fox, our UK organizer, sporting his canary yellow T-shirt, was easily identifiable at check-in. He looked slightly out of place until I noticed a file of garish shirts pushing large cardboard boxes (which housed the bikes) in the queue.

My eyes felt gritty and my limbs ached after a disastrous sleep on the plane. We were greeted at the airport by our guides, Chris and Janine Angell, whose team of Kenyan helpers steered us toward our transportation bound for the Landmark Hotel. En route, one of the bikes fell off the rack - not a good start!

Showered and breakfasted, Chris delivered the brief which listed the perils that lay ahead (potholes, dehydration, dopey drivers, etc.,). We then left for Limuru, perched on the edge of the Great Rift Valley at 7,500 feet.

And we were off! Five minutes later, the floor fell away, revealing the Valley. We flew down tarmac roads vying for space with lorries puffing clouds of exhaust fumes. Luckily, I had packed my smog mask!

We regrouped for lunch under a magnificent candelabra tree while passing juggernauts honked their horns in amusement. We cycled on a sandy track past the dormant volcano, Mount Longonot - cycling in heavy sand is an acquired skill and two cyclists wiped out.

We were rewarded by sightings of giraffe, zebra, gazelle and hartebeest. Skirting a brooding thundercloud, we rejoined the road for a 10km straight to our campsite, Fisherman's Camp, on Lake Naivasha's shores.

I awoke to a glorious sunrise at 7:10am and a number of sleepless cyclists, deafened by relentless snoring (Tent 13 had been blackballed), grazing hippos and a rowdy dawn chorus!

Our route wove through Hells Gate National Park, named after the stern cliffs that flank the entrance to the Reserve. We saw Rock Hyrax and a rare breed of vulture, called a Lammergeyer. After lunch, we cycled to Elsamere, Joy and George Adamson's outpost popularized worldwide by "Born Free." Overlooking Lake Naivasha, we ate a sumptuous cream tea and fed the resident Colubus monkeys.

The insomniacs rose even grouchier due to the phantom snorer! My colleagues pointed out that my back looked like bacon, sunburned on both sides of a white patch in the middle where my Camelbak had sat!

After negotiating a treacherous dirt track peppered with gaping potholes (Matt did an unacrobatic somersault over one, taking a nasty gouge out of his leg), we lunched after 41km on a hillside overlooking Lake Elementata, and soon discovered we were two short - Nick and Gerard overshot a checkpoint and added an unnecessary 15km.

A slow puncture dogged me for the final 12 kilometers but the group banter kept us motivated. At the finish line, the stopwatch showed 3hr 17mins.

The potholes had taken their toll and with the sun tipping 28°C, we flopped to the ground exhausted. It amazed me to see Kenyans cycling past with woolly bobble hats on! It must be like wearing an Arran knit in a Turkish Bath!

We were rewarded with a magical tour round Lake Nakuru National Park, with spotting leopard perched 40 feet off the ground in acacia trees, male and female lions and a family of black rhino. Most impressive were the thousands of flamingoes that fed on the lake's shores.

I slept off a crushing dehydration headache and rose early to leave our campsite at the Rift Valley Motor & Sports Club. Presently, we were cycling through huge sisal plantations taking regular pit stops to regroup so that no one got lost.

Mary, our 60 year old, retired early - her hybrid bike not suited to the rocky terrain. The track, where suspension really paid dividends, demanded intense concentration and sheer strength not to come off. I, like many of the others, started suffering from severe vibration numbness in my fingers, due to constant pressure on the brakes.

We crossed the equator and after one hour and 40 minutes, took a lazy lunch. A few were really suffering in the stifling heat of the lower altitudes, but our minders hopped around with cooling spray guns. Most of the group took dioraylte to combat fluid loss.

We cycled through Maji Moto where the thermometer tipped 38°c. Here we made a scheduled stop at the local school. They put on an impressive display of traditional singing and dancing and in gratitude, we handed out pens and pencils which were like gold dust.

As they sung us off, we sped down boulder-strewn descents towards Lake Bogoria, our northernmost point. The small inclines of the last 12km were worsened as fatigue crept in. I stopped to look at a turtle which proved a mistake as my legs cramped and I felt my energy levels drop off immediately. The hotel was a welcome sight and we headed straight for its natural hot spa which eased our aching limbs. We had dropped approximately 4000 feet in one day.

I noted how much fluid I consumed in the day: six liters of water (Camelbak); three glasses of lemon squash; one dioraylte; six cokes; and, three orange juices!

We began at 7,000 feet above sea level on a breathtakingly scenic spur of the Great Rift Valley. We hauled ourselves up lung-bursting climbs but every time we rounded a bend, there was yet more uphill to climb. Lungs cried out for oxygen in the thin air and my thighs felt like hot metal ingots. Some hills were too steep to cycle so we resorted to pushing our bikes.

After an unrelenting five kilometer stretch, I saw the bike rack by the side of the road. Whooping with joy, I turned into the layby in third spot. It had taken one hour and 40 minutes to cover 27 kilometers and ascend to 9,000 feet above sea level...and this was only lunch. It took 40 minutes for the tail to arrive and, collectively, we were a sorry sight, cursing and collapsing in a mixture of exhaustion and ecstasy.

After lunch, we spiraled down 4000 feet over the next 30 kilometers around sidewinder bends - those with speedometers registered 49mph. After 60km we stopped at a river crossing where we flopped into the icy waters - a few Kenyan washerwomen giggled at our horseplay.

A few of us slipstreamed each other to minimize the effort of the final 20 km. An electrical storm unleashed a violent downpour which was initially rejuvenating but after a while debilitating.

After four hours and 27 minutes of cycling, we cruised over the equator again. However, the trip on someone's speedometer showed only 99km so we pushed 500 meters further, hung a U-turn and crossed the equator for the third time to rack up the 100-kilometer target!

I woke at 6:15 to a crisp dawn. A number of injuries had surfaced during the night - locked joints, nosebleeds and "Delhi Belly."

We sought assurance that there were no more hills. Chris replied, "There are two, no three, maybe four depending on what you call a hill."

Almost immediately, we hit a hill! But then we cycled down a dusty lane that scythed through enormous tea plantations, a subtle aroma of tea filled the air. After a snaking, steep uphill, we hit a long downhill to Limuru, our start point six days previously.

I tried to crouch into an aerodynamic position for the downhills but my arms were so full of lactic acid that it was excruciating. The finish line was now almost in sight and those with speedos counted down the kilometers! With Chris leading in his 4x4, we tailed tire-to-tire into Nairobi's outskirts along the main road.

Our destination was a market place, and typically, this was at the top of a hill! One final toil to reach the top and after one hour and 41 minutes, we were there. Finished. Done. Dusted. YES! What a feeling. Everyone was embracing, shaking hands, slapping backs, such was the feeling of elation and kinship. We had suffered and conquered and no one could take the moment away from us. We looked like soldiers completing a tour of duty — grimy, tired, but beaming with self congratulation. Everyone was a hero!

I borrowed a line from a film to leave in the visitor's book - "What does not kill you makes you stronger." That, to me, summed up the essence of the challenge.