All work and no play has made Jack, or in my case Dick, a dull boy. There's only one thing for it: to shake myself out of my torpor with a dose of high-octane adventure sports. Crisp mountain air is top of my agenda, along with canyons, cliffs and vertiginous geographical features of every description to climb, hike, bike, or throw myself off with reckless abandon.
Interlaken in Switzerland's Bernese Oberland is my destination of choice. The town lies under the talismanic but often tragic spell of the Eigerwand, otherwise known as the North Face of the Eiger, and has been a honeypot for mountaineers and adrenalin junkies for generations. It's built around a maple-lined park between two lakes (Inter-laken, you see) called the Brienzersee and the Thunersee, and is a model of architectural decorum. But the true stars of the show are the titanic peaks that soar above the valleys below and make for some of the most arresting mountain scenery on the planet.
The local transport system, one of the most efficient in the world, includes the Jungfrau Railway which tunnels through the Eiger itself before emerging at the Jungfraujoch, the 3,454m self-styled "Top of Europe".
On my first morning, I join a group of 15 mainly twentysomethings in the Chli Schliere Canyon, reputed to be one of the best canyoning canyons in Europe. I'm swathed in 5mm Neoprene, and clutching a helmet and climbing harness. After a detailed safety briefing, I find myself staring nervously into an abyss as water thunders around me.
Things rapidly turn cold, precipitous and very, very slippery but within minutes I'm having the time of my life. My head is beginning to clear; the adrenalin starting to flow.
"This is one of nature's more extreme fairground rides," says Ian, one of our five guides. "The canyon is basically a series of slides, pools, ledges and drop-offs but we descend in stages. We don't ask you to jump unless we know there's plenty of water depth below – and we have ropes so you can abseil down if you think the leap looks too high."
Our first obstacle is a slide or channel in the rock known as a flume, which, as I whizz round a corner into the seething torrent of a whirlpool below, feels a bit like being flushed down a giant-sized loo. A short scramble later and we are peering over the top of a 15-metre waterfall.
Canyoning, I soon discover, is a mix of swimming, jumping, scrambling, climbing, slipping, sliding, abseiling and using foul and abusive language with a huge grin on your face. At other moments, during brief pauses in the madness, I look up to see rainbows forming around the silver birch trees clinging to the side of the canyon and gaze out over spectacular views to the valleys below.
The next day I swap Neoprene for Lycra and head off on a mountain bike to the nearby Lauterbrunnen valley, one of the largest nature-conservation areas in Switzerland. This is thrilling biking country, surrounded by mountain peaks and vertical walls that plunge as straight as a plumb-line towards the valley floor. I meander aimlessly, safe in the knowledge that if I tire or get lost, the trains and gondolas that connect even the smallest mountain villages will whisk me and my bike to wherever my fancy takes me.
My haphazard route leads me to Stechelberg at the end of the valley, where I take the gondola to Mürren and an easy red trail to Winteregg. Here the fun begins in earnest as I thunder down some challenging single-track through the forest to Isenfluh, and then by the river alongside Alpine meadows back to Lauterbrunnen. There are 72 waterfalls in the valley, the best known of them being the Staubbach Falls, with a 300m continuous drop making it one of the highest in Europe.
But an even more extraordinary sight awaits further down the valley. As I emerge from under some trees I hear a "whumph" high above me, as a parachute opens and swoops down to earth. Further investigation reveals that I have timed my ride to coincide with a base-jumping competition. Competitors are hurling themselves off the cliffs above clad in aerodynamic "squirrel" suits before free-flying into the centre of the valley like Superman and opening their parachutes
Inspired by this aerial insanity, the next morning I sign up for a tandem parachute jump. As luck would have it I have chosen a perfect blue-sky day; as we arrive at the airfield the last wisps of mist are still clinging to the surrounding pine forest. There are nine of us on the plane. We circle ever higher to the moment at 4,500m when the door will open and it will be my turn to shuffle to the exit and hurl myself out of the door attached to Mick from Queensland, my tandem freefall pilot.
A moment of terror, as the door is opened and we brace against the slipstream, the wind howling in my ears and my stomach gyrating like a washing machine on max spin. Then with a "hard arch" we plunge out of the door. Nothing prepares you for the rush. Within seven seconds we reach 200km/h – the speed of a Swiss high-speed train – and my stomach is doing weird stuff I never realised was possible.
I have just about enough time in our 40 seconds of freefall to get my senses together and take in my surroundings. In the distance framed by a deep blue sky I can see the Eiger, the Jungfrau, the Matterhorn, and even Mont Blanc over the border in France. To make it even more surreal, a crescent moon still floats serenely above them all.
On my final morning in Interlaken, I take to the skies once again on a much more gentle tandem paragliding flight from a mountainside to the north of the town. This time we defy gravity and fly upwards as the canopy inflates and we glide out over the valley. One thousand metres below, the cars look like Dinky toys and the wake from the pleasure cruisers on the lake resembles brush strokes of white paint on the surface of the water.
In my flying armchair I am able to take in the view at my leisure. To the south is the Schilthorn with its revolving restaurant where the Bond film, On Her Majesty's Secret Service, was shot, while the now-familiar profile of the Eigerwand looks as intimidating as ever. Then we drift down into the centre of Interlaken and land on the patch of green outside the Metropole Hotel.
After an adrenalin-filled burst of all play and no work, Dick is no longer a dull boy.
Travel essentials: Interlaken
* Neilson (0845 070 3466; neilson.co.uk) offers seven nights at the Hotel Metropole in Interlaken from £785 per person, including flights with British Airways from Heathrow to Zürich or Basel, breakfast and transfers.
* The nearest airport is Bern, served by SkyWork Airlines (00 41 31 960 21 94; flyskywork.com) from London City. Otherwise Interlaken can be reached from Basel, Zürich or Geneva.
* Hotel Metropole, Interlaken, Switzerland (00 41 33 828 66 66; metropole-interlaken.ch).
* Outdoor Interlaken (00 41 33 826 77 19; outdoor-interlaken.ch) offers canyoning, paragliding, skydiving and a high ropes course, all of which can be pre-booked through Neilson.
* The Interlaken region (00 41 33 826 53 00; interlaken.ch) also has 160km of well-marked mountain-bike routes and is well serviced with bike-rental options.
* Switzerland Tourist Board: 00800 100 200 30; myswitzerland.com