It’s snowing and I want to swim. Really, freshly bold from my first wet-suit free swim, I want to find a snowy pool somewhere where I can plunge then lunge for my clothes again, but doing that alone isn’t smart. And so I head for an as-yet un-swum (by me) lido – the pool at London Fields.

The air is frosty and the paving stones crackle beneath bare feet, wince-inducingly cold. The sky is milky, so full it doesn’t stop anywhere. No start, just billowing, smoke-like white contained somewhere up overhead. The water, by contrast, is full of life – both in colour and in crowds. Human bodies rove up and down, thrashing, smashing white waves through the water. So many swim hats, so many waving limbs. The thing I love about my local lido is the opposite of this – it’s often much quieter than indoor pools. But this is something else. Even on a snowy day, it’s heaving.

I join the cycle of swimmers anyway, and plough up and down. The water is frenetic with overtaking and flippers and swim floats. After a bit I sidle into the slow lane, push my goggles to my forehead and kick along with my head raised to feel the cold caress my cheekbones. Without the steamy goggles, I can see the steamy sky. White ribbons rise from the water to pool and dance in the air. The bright changing huts are muted by the magnificence of the heat escaping into the thickened atmosphere all around us.

I’m raising money for the Alzheimer’s Society. Please sponsor me at http://www.justgiving.com/swimbonnieswim