“Hampstead Heath, and its enlightened management by the City of London Corporation, makes a useful working model of good practice both in terms of pollution and access. The Highgate Ponds, fed by chalybete springs high up in Kenwood, descend the hill and are segregated by tradition into the Women’s, Men’s and Mixed Ponds. Entrance is always free, there are simple showers and changing sheds, and each pond is maintained and observed by lifeguards.”

The buoyant waters of Hampstead Mixed Ponds are sadly skipped by Roger in Waterlog. Instead, he takes a dip at the nearby Highgate Men’s Pond, where I braced myself for the cool waters late last autumn and throughout this chilly spring.

But I feel they warrant inclusion here. They are, after all, referenced by Roger in his 2001 Open Democracy article, written as Waterlog was published. I’ve also come to see them as my version of Roger’s moat at his Walnut Tree Farm home. A place to escape to for a swim when further excursions aren’t possible. A spot where I can digest the swims of recent weeks while escaping London’s never-ending thrum.

Last week I made my way from my home in south London to Hampstead Heath twice. Once before my dip in the Waveney at Mendham Mill and again a couple of days after. What I tend to find at the Mixed Ponds is that no two swims are the same.

I always think this is largely down to the fact that it’s an oddly shaped space. You can swim to the far rope and back, but you won’t manage to do it in a straight line or get from one end to the other without having to attempt to swerve someone lolling on their back in an aimless stroke.

This makes it special, as does its sheer popularity. Come here in summer after 2pm, and finding a place to ditch your bags is tough. There’s always a queue to get into the water and always one of water-treading swimmers waiting to get out. But dive in, swim 10 metres, and you’re in a blissful bubble. The fact my phone has never managed to get reception here makes it all the better. The Mixed Ponds are an escape route that usually only rural swimming spots afford me.

On my first visit last week, I arrived at 11. The place was relatively quiet, the heat of the day just rising. My friend Joe and I swam eight lengths of the pond, each one slightly different. Water boatmen skated across the surface, the occasional dragonfly danced in front of me as I made for a nearby buoy to take a quick rest. The water was slack as ever. That feeling of never being able to touch the bottom makes this a swim that never stops. Pauses are infrequent and rarely satisfactory. But it’s that which makes swimming here so perfect. You have to keep going and can therefore take more time to keep losing yourself.

A few days later, I returned at lunch time with Molly. This time we swam back and forth and chatted about wild swimming, about skiving off afternoons to take a dip whenever we could find the opportunity. This is Hampstead, and open water’s, other delight. It’s a social experience like no other.

I often think about Roger’s moat when I swim here. How he always returned to it after a long trip away to Scotland, Wales or the West Country. I don’t have the luxury of schlepping across my lawn to my own outdoor swimming hole. But Hampstead Mixed Ponds comes very close.