‘At first I’m terrified – this really is very fast and high’

longest in Europe, stretching for a whole mile, 500ft above ground. Pootling along upright enjoying the view of Horseshoe Falls this was not.

Waiting is always nerve-racking, and there’s plenty of it to be endured here. Once it’s time for our slot, an instructor takes the group to be kitted up in fetching red boiler suits, harnesses, helmets and goggles. A pouch at the front can hold phones, so you can snap away. As I glance apprehensively up to the mist-covered peak we’ll soon be heading up to, it’s hard to resist the temptation to ask for another final check of my equipment.

From here, it’s on to the Little Zipper, a dry run for its Big sibling. This got me in the mood nicely, but it could have quite the opposite effect on a more nervous flier. Once everyone has cleared this first hurdle, we pile on to the back of a small, open-sided truck for a bumpy, windy ride up to the start of the Big Zipper.

The views from here are spectacular, even on a cloudy day, taking in mountains and ocean, and beneath you the slate quarry, 1,200ft deep. Getting on to the wires themselves requires one to be quite physically agile – I have to lower myself down ungracefully into a press-up position with my bottom in the air before I can be hooked up. There are two parallel lines so that you can ride in pairs; I crane my neck and catch a glimpse of my girlfriend’s terror-stricken face, evidently wondering what on earth possessed her to agree to this. With the landing base radioed and ready to receive us, there’s a threetwo-one countdown, and we’re off! The steam inside my goggles vanishes immediately, leaving me with a clear view – though at these speeds, it’s hard to take it all in. It’s difficult to describe what travelling at speeds approaching those of a plane at take-off feels like, but imagine a classic cartoon face-blasting and you’ll get the idea. At first I’m terrified – this really is very fast and very high – but as I glimpse the calming blue of the water at the bottom of the quarry, I begin to relax and enjoy the ride. It’s so exhilarating, more like flying than anything I’ve done before, that I have to resist the urge to bellow (we’ve been asked to keep noise to a minimum in the early hours for the sake of nearby residents).

Depending on your weight, you either travel pencil-like, or with your arms out; I start as a pencil, but put my arms out when I see an instructor signalling for me to do so as I approach the end. I’m ready for the dismount, having been prepared by the Little Zipper, and being flung into a swinging halt does not come as a shock this time round. As I’m lowered down I start to laugh, whether out of delight or relief, I’m not quite sure.

One ride on Velocity costs £70, which is a lot, given that the Big Zipper ride takes less than a minute – that’s more than a pound a second. That said, the whole visit takes about two hours and you also get to experience the Little Zipper, the ride up and the views from the top.

For true daredevils, it might not be quite perilous enough to justify the cost, but if you are after some relatively risk-free thrill adventuring, it’s perfect.