“By the time we were into the black water it was just after midnight. There would have been a moon, but there was too much cloud. Nosing through the luxurious water, we swam under a faint curtain of rising steam that hung just an inch or two above the surface.”

Smudgy grey cloud has already darkened the day, and as I emerge onto North Hill, I’m cast further into shadow. The white walls of High Point, clad in vertiginous scaffolding, loom over the road, making it feel more like dusk than mid–morning.

I’ve taken the Tube up from my south London home to meet Lucy, resident of this spectacular Lubetkin–designed block and a friend of Roger’s who swam with him both here and in the hefting waters of the North Sea at Walberswick.

I make my way through the clean lines of the lobby and into the central lift. Caged, yet open, I think of Connery’s James Bond tussling with a baddie in Diamonds Are Forever in a similar space in an Amsterdam townhouse. Thankfully I remain unharmed as I emerge on the fourth floor and the double doors of Lucy’s flat open to the sound of the elevator’s final clank.

Lucy has lived in this corner flat for 15 years. She makes tea and we sit and talk about swimming: her love of striking out towards the horizon from the beach (something Roger mentions in Waterlog) versus my preference for staying close to shore, swimming parallel with the rolling waves; the coldness of rivers in September; and the joy (or otherwise) of wetsuits and neoprene.

The private pool is just about visible from Lucy’s living room, high up above Highgate and I can  make it out beyond the tennis courts and neatly manicured lawn. Lucy isn’t joining me in the water today, but any guests swimming must be accompanied by a resident, so she leads me down the swooping spiral staircase, around the lift shaft and out into the gardens.

A drizzle is just starting up as we pick our way through the borders and flagstones and through a gate held fast with a Yale lock. Lucy lets us in and points me towards the changing block while she takes her book underneath a Yew tree in the far corner.

Having access to a private pool like this is my idea of heaven. Lucy swims here every day and it’s easy to see why. The cosy changing room alone is better than any of the rough and ready rooms where I’ve laid my bag and coat over the past few summers. Emerging in my shorts and goggles clamped on, the rain is properly coming down and I waste no time in dropping in at the deep end.

The water is blessedly warm, in the high twenties if I had to guess. Not so cloying that it makes you sweat, but cosy enough that you can swim on and on without fear of your internal organs going into shutdown.

I quickly settle into the rhythm of front crawl and lose myself in bubbly breathing. There is something joyous about swimming in the rain. Usually miserable weather sours my mood, but when it starts teeming down and I’m in ensconced in the water, I feel an added frisson of elation. I’m already wet, so the weather can do as it pleases.

I think about everything and nothing. My journey here, the journey home. How London swimming has changed beyond all recognition since Waterlog was first published: lidos reopened, swimming spots rediscovered, the Thames mooted as a new destination for my fellow open water fanatics.

After a pleasant thirty lengths, I emerge reinvigorated. I shower off, get dressed and meet Lucy for the walk back to the foyer. The London leg of my journey is at last complete, more than two years after my first capital dip. Strolling back towards the Tube, I count the remaining swims on one hand and let my already soaked head get even more drenched in the now incessant downpour.

With thanks to Lucy Moy Thomas