“Let’s go swimming” we said. “In January”, we said. “Outdoors, without a wetsuit.”

Back in the summer, it seemed a good idea to enter the Cold Water Swimming Championships at Tooting Lido. The championships only take place every two years. Couple that with the fact that places sell out faster than a polar bear chasing a seal, and before we knew it we were signed up.

When I say we, I mean myself and Katie who I blame entirely, her friend Charlotte (left) and Josie (right). Like any good swimming gala, there are a few categories to choose from. We opted for front crawl, certain it would get us to the other side of the pool and out again the fastest. Only Josie was too late to grab a spot in the freestyle, so she had to plump for ‘heads-up breaststroke’ division.

The water was 3.5C, and we’d have to swim 30m whatever stroke we were doing.

The military precision with which the event is organised has to be admired. At registration I was handed a lanyard which told me to muster a good 20 minutes before my race, for which I was given a start time that read to the second. The stewards meant business in getting all the heats set off on time.

I was not looking forward to my race and thought there was a good chance that I might not even get in the pool. But there was little opportunity for backing out. After mustering, my heat was shepherded round the far side of the pool and told to get changed and put our belongings in a bin bag. This felt a bit like either prison or hospital and I wasn’t sure which was more appropriate for what was about to happen.

There were seven other women in my heat, which seemed an ironic word for what was about to happen. I was in lane 5. “You’ve been seeded!” Katie joked.

We moved round the edge of the pool as a group with our belonging in a bin bag. I trailed behind the others still trying to put my swim cap on. We were briefed: “No diving. Get in and put your shoulders under straight away. The race won’t start until everyone puts their shoulders under. Nobody wants to be the person that makes everyone else hold under the water.”

Our names were called out over the loud speaker by the announcer and the crowd cheered. It was all feeling a little bit professional and my swimming would be anything but. I’d been watching the earlier heats and I hadn’t seen a single person back out. I felt like a racehorse who was about to refuse the start of its race.

In a whirl of being told to stand here, go there, take that off and get in, I was blindly following orders shouted at me and, before I knew it I was in the pool and my shoulders were under. I was shocked by the coldness of the water and it took me a moment before noticing that the marshal next to me was shouting for me to hold onto the bar. They wouldn’t start the race until I held on.