“Pour some coke on it” said my friend Josie. “That’ll kill any bugs.”

“Yes! It can clean a 2p piece so it’ll clean your foot” chipped in Helen.

The first open water swim of the year also means the first wearing of plastic flip-flops of the season. I’d met Josie from the tube and we’d speed flipped and flopped our way to the Ladies’ Pond on Hampstead Heath to meet Laura and Helen. A mile and a half of power walking had done more damage to my feet than the two marathons I ran last month combined.

We all lowered ourselves into the water. It was 13C and with our wetsuits on, it wasn’t too bad. Helen, taking her wetsuit for its maiden voyage, hadn’t swum in a lake before. I’d invited her along for a swim because, not so long ago, my friend Katie took me for my first lake swim and I know how less scary that made it.

Katie and I are guiding some novice triathletes (including Helen) through their first season this year and, although I sometimes feel a bit of a fraud dishing out advice, it’s nice to share a bit of what I’ve learnt over the past couple of years.

We swam a few laps of the pond, our hands and feet getting used to the water temperature and at the icecream face slowly subsiding. While we swam safe and snug in our wetsuits, women were getting in wearing just a cossie and without making a fuss. One day I’ll be one of those women, but not today.

Laura had brought along four cokes for us all to have after our swim – an open water swimming trick to hopefully kill off any bugs in your stomach. If the marketing bods knew this there’d be a summer advertising campaign with a red truck rolling into towns driven by a guy in a red wetsuit singing “Open water’s coming, open water’s coming….”

My flip-flop injury had broken the skin, and so this is how I came to pour coke on my foot.

“Argggggghhhhh! That’s worse than TCP.” It stung. A lot. “If that’s what it’s doing to my foot, imagine what it’s doing to our insides.” We polished off our cans all the same and headed off to get icecream and hot chocolate.

The turn from April to May marks the change from running long distances to a summer of running short fast stuff and swimming outside. I have my first triathlon of the year on Sunday at Crystal Palace and an open water swim race the following weekend. But I’m not quite done with running long just yet. I’ll be heading to Copenhagen at the end of May for one more spring marathon. And, hopefully, I’ll be running long as well as fast.