The class, called AquaFit, was held in Canary Wharf, which seems to have the highest concentration of luxury gyms anywhere in the capital. In fact, it’s mainly luxury gyms, as far as I can tell. And this one was as luxury as it gets. The entrance hall looked like the lobby of a five-star hotel. In the changing room, staggeringly beautiful women blow-dried their immaculate hair, sitting in front of the mirrors in their matching underwear. ‘You don’t belong here!’ Old Me jeered, in my head. Old Me was delighted that I’d finally got my comeuppance. I was getting nervous – what had I signed up to?