I tricked my Mr into going to climbercise with me by pretending it was like bouldering (which he does), only with ropes. In fact, it was like circuits, only with ropes. No, wait, it was like climbing, then doing circuits, then doing more climbing, then doing more circuits. I also booked us in to see jazz afterwards (there’s a club around the corner from the gym). It was like the 12 Labours of Hercules.

Top rope climbing is where you have a belay, a friend-come-counterweight at the base of the wall. Automated top-roping is where you have an intensely strong elastic (or whatever; I don’t want to talk about physics) that simply guides you down once you’ve got to the top. It’s extremely fun, which is why, if you’ve been to a Clip ’n Climb centre, it’s likely to have been for a children’s party, because it’s like bungee jumping without fear. As a fitness pursuit, it’s still worthwhile, since all the effort is in getting to the top, whatever kind of climbing you do (potential energy, obviously; oh, it appears that I do want to talk about physics).

The first half-hour was a free climb, which I took very easy, having an inkling of what might be down the line, and which Mr took very energetically. With an hour to go, we were divided into three groups, one doing cardio (running, bear crawling, running, jumping); one still climbing; and one doing resistance – squats, bench hops, a sit-on-the-bench-then-jump manoeuvre. “It looks like a fringe mime production about commuters,” I said. “I’m just another number. Wait, I feel alive! No, I’m just another number.”

The instructor had done a marathon the day before and was in no mood for shirkers. “Are you two meant to be bear crawling?”

The cardio was fine. The bench hops were extraordinarily difficult, and I claimed to need the loo, which takes a long time when you’re pretending to remove a climbing harness. The climbing, which in regular life is quite strenuous, was a huge relief after the rest of it. This, I guess, is the USP of the class, or it would just be 90 minutes of pain and nobody would go.

When I pointed this out, Mr was having none of it: “Argh, you’re doing that thing where you say ‘nobody’ and you just mean you. Zobody likes yoghurt. Zobody washes their sheets every week.”

“Nobody does that.”

“Zobody does what?”

“Nobody picks three simultaneous fights in the middle of an exercise class.”

The instructor came out of nowhere. “Are you two meant to be duck-walking?”

“We’re actually quite fit,” he said, “these people are all much younger than us.”

It was sort of true, though the woman who climbed the speed-wall just before me did it 32 seconds faster (to be more precise: it took me 39 seconds and her seven). But we’d striven, for the most part, honestly, and were virtuously exhausted. Didn’t go to the jazz, though; nobody likes jazz.

Give it a go

There are Clip ’n Climb centres all over the UK – find your nearest at clipnclimb.biz.

• Hair and makeup: Sarah Cherry. Clothes: My Gym Wardrobe