My five-year-old daughter enters the river first. Elbows pumping and knees lifted high, she dashes in, her excited shrieks turning to loud yelps of surprise as the chill shoots through her.

I follow close behind, my feet instantly numb as they plunge into the tannin brown water. I find myself laughing with my daughter; laughing off the cold; laughing off the decision to go swimming at the turn of the New Year.

Grinning wildly she turns back towards the muddy beach and my wife and son who are sitting with their chins sunk deep into parkas – cradling hot chocolate and cheering us on.

I keep moving. Pushing towards the small waterfall that brings the Little Ouse into the northern edge of Knettishall Heath; my body gasping involuntarily as the water reaches my stomach. This is the slow torture of gradual immersion. I hold my breath and sink down, my shoulders and face tingling and burning with the cold. I know it’s probably just seconds, but it feels longer. Minutes. Hours even. A whole year of concerns, worries and squabbles sloughed off in a bone-chilling baptism of copper water.

I stand quickly and walk back to the bank, picking my way around heron tracks that I missed in my rush to get in.

Two dog walkers are returning to their car; stamping their feet in the cold. I can see them looking over as I gladly take the towel from my wife and wrap my hands around the mug of hot chocolate. My feet ache from the cold, but I’m happy, waiting for the glow to start – the delicious post-swim feeling that lasts a whole day; an earthy cosiness that makes your own skin feel like a duvet.