Sam is 10 years old. Having done this high wire forest course once already, he’s full of helpful advice. “Just put one front foot in front of the other,” he says on the approach to the Goat Crossing, a bridge that feels as though it’s weathered Indiana Jones.

The fact that a 10-year-old is allowed on the course should be reassurance in itself. The beauty of the Go Ape experience is that it manages to strike a fine balance between safety and fear. It’s safe enough for your mum to manage, but scary enough to be fun.

Go Ape launched in Thetford Forest six years ago, and today there are 17 treetop adventure courses around the country from Grizedale Forest in the Lake District to Moors Valley in Dorest. Five are within day-trip distance of London, and Swinley Forest is our pick of the bunch.

Less than two hours from the city we find ourselves in the Home Counties, where people say “thank you, Driver” getting off the bus and will happily give you directions. Which is lucky, as the course is well hidden in the midst of Swinley Forest, a playground for families, dogs, mountain bikers and wannabe Tarzans.

The first dose of fear comes in the form of a disclaimer we must sign in the event of an accident or fatality, then Grant – who with his bleached hair and edgy tattoos looks like an extreme sports instructor circa 1994.

“Is this extreme?” I wonder, looking up to see an elderly woman clinging to a cargo net, whimpering softly.

“The main thing to remember,” Grant tells us, “is always stay attached.” Dangling from our harnesses are two carabiners, the most important things in our lives for the next three hours.

By clipping and unclipping, double clipping but never double unclipping, we’re to negotiate a course of zip-slides, rope bridges, Tarzan swings and high wire stepping stones. After a short test run we’re sent on our way.

At first it feels like we’re wagging school – no instructors guide you round the Go Ape courses, you’re trusted to remember the training and look after yourself. For an adult constantly being told to “mind the gap” and that bags of nuts may contain, well, nuts, it’s slightly disconcerting.

Still, before long my friend and I are shinnying up ladders, gliding between the Scots pines and clipping on and off like highly cautious monkeys. At points, when I find myself unexpectedly doing the splits between two suspended stirrups or crawling through a kind of swinging, wooden tube, I’m laughing so hard I wonder if they’re piping something into the forest.

There are four sections to the course (after the test run) each finishing with a zip-slide that seems to get higher and longer as we go. How you land depends on which way you reach the bottom. If you’re lucky, you arrive head-on and pedal furiously to keep upright. If you’re not, you arrive backwards, scooping up pantfuls of wood chip in the process (to anyone going along in the near future, I apologise if your landing isn’t as soft as it once was).

Still, a few splinters is a small price to pay for a day spent feeling like a big kid, albeit one far less capable than Sam. In the simple words of one customer, impressed enough to fill out the visitor’s book, Go Ape is “totally pimp.”

Vertigo-go
Here are some other ways to get high without risking the munchies.

Iron roads
Via ferrata are fixed footholds, ladders and bridges that ease passage through mountains. They originated in the Italian Dolomites (it means iron road in Italian) to help soldiers move around during World War I, but since becoming a tourist attraction have spread through Europe. In the UK you’ll find a via ferrata at Honnister (www.honister-slate-mine.co.uk), near Keswick in the Lake District.

Bridging the gap
On the way to the Giant’s Causeway in Northern Ireland you’ll find the Carrick-a-Rede Rope Bridge. Fisherman rigged the bridge across the Atlantic to reach their salmon nets on Carrick-a-Rede island. Those brave enough can cross the swinging bridge over a 24m deep, 18m wide chasm to be rewarded with fantastic views over the sea to the Scottish coast.

Tree hugging
You might not have risked life and limb climbing a tree since primary school, but you’re never too old to give it another go. Dotted round the UK are centres that turn this kiddy pastime into an adventure sport. Try the Mighty Oak Climbing Co (www.mighty-oak.co.uk) in Cornwall or Goodleaf Tree Climbing Adventures (www.goodleaf.co.uk) on the Isle of Wight.