Back at my desk, I verified on the internet that they were indeed giant slides and that, incredibly, the general public would be allowed to slide down them. I determined to visit as soon as possible, before some silly fool had an accident and they got shut down.
Having spent today's lunch break queuing for a free timed ticket, I was allowed by my lovely boss to return for my 2:30 slot.
There are two slides from the second floor down to the first, these being suitable for children and not requiring tickets; one from the third floor, one from the fourth and one from the fifth. I had tickets for the latter three and worked my way up the building. By the time I reached the front of the queue for each slide, my ticket was creased from being twisted nervously in my fingers.
You're given a canvas mat with a pouch at the bottom for your feet and told to lie as straight as possible, fold your arms and look down at your feet. Then you launch yourself - gingerly in my case, forcefully if you're a teenage boy who will then scream like a sissy on the way down - into the first drop.
The slides are like swimming-pool chutes without the water: the vibration of the connecting joints passing along your back in quick succession gets painful after a while. Although the top half of the chute is transparent you can't see much from your prone position - especially when obediently looking down - but it's fun to watch other people going down the tubes, as it were.
The longest slide takes about 12 seconds and gets up to 30mph. I was terribly afraid my glasses would fall off, and despite crossing my arms across my chest in deference to the many safety notices I managed to bang both my elbows. Like the best roller-coasters, it came to an end just when I thought I couldn't possibly take any more.
"That was BRILLIANT!" I said to the attendant at the bottom as I shot out of the aperture, fell off the end and landed sideways on the rubber crash pad in a tangle. "The best thing there's ever been at Tate!"
"Not my cup of tea, I'm afraid," said she, folding up my mat.
I've been grinning like a loon ever since, hyped up on that fairground feeling of having survived mortal peril. I keep expecting my colleagues to ask me if I got lucky last night. Whatever else you may have been doing, I feel sorry for anyone who didn't ride a giant slide today.