In the theatre world they have a saying: Bad dress rehersal, good opening night. For a while I was taking solace in this saying, reassuring myself that my triathlon ‘opening night’ would go without a hitch. But there’s been no dress rehersal, I’ve broken all the rules about trying all your kit before race day and haven’t even taken the pricetag off my onesie yet.I’ve dragged my wetsuited self down to a lake twice now. While it quelled my fears that I’m going to sink to the bottom of the river without trace on Sunday, it hardly filled me with confidence. I swam in a pool last night for 750 meters – the same distance I’ll need to swim on Sunday. My lane at the pool was occupied by me and one other swimmer and, quite frankly, that was one too many for my liking.

Come 8:15 on Sunday morning it’s likely that my lane will be occupied by around 100 other swimmers. Elbows and feet will be flailing in all directions and this is what I worry most about. I don’t worry about my own swimming – I could slowly complete the course by myself without getting into difficulty, but I worry about the other people. That someone else will panic and grab hold of me. That an elbow to the face will knock off my goggles and make be panic. That a kick to the chest will leave me winded and unable to swim.

Fear can be a good thing. It can give you the extra adrenaline you need on race day. But it is my biggest threat when I’m swimming. The anxiousness I feel makes my chest tighten and my breathing hurried – two things that aren’t useful at any time, let alone when you’re trying to swim in a straight line and not take a lung-full of water.

I read a quote on twitter this morning, someone describing their triathlon race strategy: “Survive the swim then race like hell.” It sums up my feelings about the swim quite neatly. Though I’m counting the bike as the ‘race’ part and the 5k run as more of a victory lap if I manage to make it through the previous stages unscathed.

I’ve joked a lot about being worried about the swim, but it’s no exaggeration to saw it really does scare me. But as I lower myself into the water on Sunday, I’ll be thinking of Chrissie Wellington and the promise I made to her. I’ll also remind myself that however badly my triathlon debut goes, it won’t go as badly as Chrissie’s – her wetsuit filled with water and left her unable to swim at all. That really was a bad opening night.