Since my last column I have been obliged to acknowledge the passing of my 59th birthday. They say you should slow down as you near those threescore years; realise you're not as young as you used to be; accept the passage of time with dignity.

What balls. These past two weeks I've been celebrating with a trip to Colombia, whence (if we make it past a landslide tomorrow morning) this diary comes. I've been alligator-chasing, tree climbing, zip-wiring, abseiling, caving with vampire bats, white-water rafting, off-roading, paragliding, subterranean tombstoning, horse riding and eating roast ants. You really have to try them.

Tree hopping

Where to start? In the Amazon jungle, where a half-day ride in a motorised canoe from Colombia's river port - Leticia - took us down the Amazon itself, then miles up a tributary, deep into virgin forest. After resting in palm-thatched cabins at the Reserva Natural Palmarí, we set out by night in search of caymans. It's amazing how, when you spot one of these alligators from your canoe, you can just plunge your arms into the water and yank it out, holding it by the neck so it can't bite.

Admittedly I left this to our guide and received the creature myself (it was about 2ft long) to pose with her for a photograph. Then we returned her to the riverbank where, to the shriek of frogs and night-insects, she shot off into the blackness of the forest undergrowth.

Next morning my friends and I climbed a 200ft rope, using special climbers' clamps, to a wooden platform in the tops of a giant tree, pausing for breath before clambering along a rope-suspension walkway - the magnificent forest canopy beneath us - to another treetop, from which we zip-wired (sliding on a harness on a pulley strung from a steel cable) to a third treetop, from which we watched an extravagant Amazon sunset, then abseiled down into the firefly-pricked gloom of the forest floor.

This was such fun that we repeated the canopying experience at our next jungle lodge, in a Colombian national park called Amacayacu, by the Amazon. My nephew James was bitten by a monkey. How I envied him. With luck he'll have a scar.

Water boiling

The rafting was something else. By now we had left the Amazon for the province of Santander. Here one of the world's greatest canyons cuts itself some 5,000ft down into the green and yellow mountains where a raging river winds its way between massive rock flanks. We rafted in inflatable craft for about 15 miles. I shall not forget the contrast between short interludes of violent motion as the river boils and roars and you dig your toes into toe-holes and paddle for dear life, and long stretches of glorious calm as you slide silently between sunny cliffs.

En route back to our beautiful little hotel in a colonial gem of a stone-paved town called Barichara, I noticed a big stone fountain, delicately carved, for sale by the roadside.

Something came over me. Now to organise shipping to Derbyshire.

Blind divebombing

Now where was I? Ah yes - about to go caving. This, I should mention, followed something they call rappelling. You abseil down from the lip of a waterfall to the base, spider-walking down the rock face, inside the waterfall. Ours was 220ft high. Fantastic.

And it prepared us for the cave. You zip-wired from a hillside into the huge mouth of the cave, where a river entered. Then splash and crawl your way through the tunnels, encountering seven species of bats, including one vampire species. Sadly I was not bitten. When the cave-river drops over a 15-foot lip into a big pool, we leapt into the blackness, divebombing into the dark - splash - deep inside a mountain.

On the way back I bought a lorry tyre, converted with knives and bright enamel paints into a toucan that you can hang from a tree and swing from. We also stopped to buy a bag of roasted ants. Delicious when salted.

More rum do's

I could tell you about yesterday's horse trekking through mountain forests (I couldn't ride; can now, sort of). And I forgot to describe my 30 minutes' paragliding, wheeling with vultures from the edge of that canyon. But I've run out of words. And the others are all off to a mountain pool fed by hot volcanic springs, with a bottle of Colombian rum. They say there's one age everyone would like to stay for ever. I used to think mine was 18. Now I know it's 59.

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