FOOTFALL. It's not really a word you want to be hearing minutes before climbing one of London's slipperiest-looking landmarks.

Alistair Wood, the man behind Up at The O2, is explaining the background to this unique new attraction, and it seems boosting the venue's relatively minuscule number of day visitors is a key motivator.

"The Sydney Harbour Bridge climb was an inspiration for us," he continuess. "But this is altogether different."

The build-up, fittingly, is wonderfully over the top. You enter Base Camp, which is adorned with great swathes of completely redundant ropes, carabiners and barometers.

From here, it's into the Expedition Climbers Training Hub, a Nasa-meets-Ikea briefing room, for earnest health and safety talks and a video exhorting you to From here, it's into the Expedition Climbers Training Hub, a Nasa-meets-Ikea briefing room, for earnest health and safety talks and a video exhorting you to "conquer the O2" (all 52m of it).

Staring down from the wall of the kit room, where I'm prised into a futuristic climb suit and harness, is Sir Edmund Hillary. He looks bemused.

Belongings go into a box, prison style, there's a final safety check, a few high fives and then we walk out in slow-motion to the waiting shuttle. In fact, it's a tramp up some steps to the starting platform, to one side of The O2's neon-lit main entrance.

The fabric walkway extends above me, a blue ribbon wrapped around the distended white belly of East London's big top. At its centre, like an extravagant belly-button ring, is the steel viewing platform, the summit. Will we make it? We're pretty sure we will.

With a gradient of almost 30 degrees, the outermost segments of the 350m-long route are the most strenuous yet eminently manageable. The incline flattens off in stages as we advance, dragging our Latchways harnesses along the central safety wire like they're recalcitrant toddlers.

The walkway is suspended slightly, generating a space walk-style wobbliness. It's a strange sensation, part bouncy castle, part ski slope (bring your sunglasses; the reflected glare can be dazzling).

We unhook at the oval viewing platform and have a wander. There's a wraparound strip engraved with a bit of historical information and some guff about mudlarks.

You'll be more concerned with greedily bagging London landmarks. They're all within sight: the glinting, dhow-like curves of the Thames Barrier; Greenwich's incomparably grand architecture; the London Eye; the mini Manhattan of Canary Wharf, surprisingly close. The views are spectacular and ever-changing.

Jets nipping in and out of City airport just to the east; Thames Clippers plying the arc of the river; diggers at the Olympic Park, just across the water. For the disorientated, there's even an app with site recognition.

Of all the stars who have played The O2, only Bon Jovi made it this far, playing a promotional gig here in 2010. Rumours that Prince didn't pass the 1.2m height restriction are unsubstantiated.

It's difficult to tear ourselves away but, as Hillary knew only too well, the top is only halfway.

Footfall? Prepare for a stampede.

INFORMATION

Up at The O2 (0208 463 2000/ theo2.co.uk/upattheo2) offers 90-minute experiences from £22.