After a cloud-spoiled summer, September was stifling in London. It was hot—almost too hot. Even Harry Styles left his aerie next to the Spaniards Inn to take a dip in Highgate Men’s Pond on Hampstead Heath. As ringing an endorsement as Styles’s appearance was, it’s not for me, I’m afraid. I like the balmy waters of the Mediterranean, as opposed to the brisk murk of the Pond, but here you will find London at its most relaxed and leisurely, enjoying the lulling change of the seasons.

In summer, the Men’s Pond is the epicenter of gay life in London. When the heat rises, men of all ages sunbathe and chat on the lawns surrounding the water. Hampstead Heath is a vast, and storied, cruising ground. Even after homosexuality was legalized, in 1967, the Heath has remained a site of covert assignations beneath the beech trees—George Michael used to hook up there—although these assignations are not always sexual ones.

Congregating on the “Beach,” the southwest-sloping grass field bordering the Men’s Pond, a colony of mostly young gay men disport themselves in the briefest of briefs. The atmosphere is generally convivial. While listening to the popping of prosecco corks, all seem to share in happy times on these grassy strips.

Fifty yards away from the Ponds is Millfield Lane, a short, leafy street of multi-million-dollar Georgian cottages and modernist palazzos. That is, until you get to No. 44—a dull, six-story office block with filthy windows that abuts the eastern boundary of the Heath. Set back from the road, the building bristles with CCTV cameras and satellite dishes. It is a slab of the Cold War marooned amid North London luxury.

Built by the Soviet Union in 1957, 44 Millfield Lane is home to the Russian Trade Delegation, which has been a den of spies for more than 80 years. As with the London gay community, these spies have used the Heath as their playground, for dead-letter drops and secretive meet-ups. I’ve been fascinated by this hulking compound since I moved up the hill from it two years ago. The gates are always locked shut. The padlocks gleam. You never see anyone go in or go out. But the Russians are still there, and they’re still being closely observed, not just by me.

Just visible behind the wire fencing and security cameras on the quiet upper reaches of Millfield Lane sits the Russian Trade Delegation. Its gloomy and inauspicious countenance betrays its secretive purpose in accommodating a nest of spies, often expelled in the old tit-for-tat reciprocals of the past.

One night, I saw a discreet young couple parked in an Audi Quattro 20 yards from the gates. As I walked past it the car roared to life and screeched into the night, hurtling round the corner with terrifying speed. When it comes to watching the Russian Trade Delegation, all subtlety is suspended. After the botched poisoning of Sergei Skripal, a former Russian military officer, in Salisbury, a helicopter flew over the compound every day at the same time for weeks.

As the war in Ukraine has rumbled into its second year, the Russians have gradually retreated from sight. The local community has made its feelings known. A nearby roundabout has been renamed Boris Nemtsov Place, after the Putin opponent who was gunned down near the Kremlin. And yet nearly every non-Russian resident I spoke to about 44 Millfield Lane insisted on a condition of total anonymity. For, if I can generalize, the British people—on a personal and governmental level—are terrified of Russians. The chance of assassination. The possibility of nuclear Armageddon. The icy-cold steppes.

A dull slab of the Cold War marooned amid North London luxury.

One of those willing to talk on the record was Trevor Abrahmsohn, the managing director of Glentree Estates, a real-estate company “to the rich and famous” that happily advertises as selling properties “to some of the wealthiest people in the world including oligarchs.” Abrahmsohn helped sell Witanhurst, the second-largest home in London after Buckingham Palace, to Andrey Guryev for $50 million in 2008. Guryev is now subject to U.K. sanctions.

Abrahmsohn is a charming presence. He tells me how the location of the Russian Trade Delegation—and the reassuring presence of Karl Marx’s grave in nearby Highgate Cemetery—encouraged Russians to come to this part of London in the early 1990s. He says the clean, cool air and shuttered privacy of the area’s housing reminded many Muscovites of their summer dachas. But now, Abrahmsohn tells me, “activity among the Russian market is practically zero.”

At the upper east corner of the Heath lies the recently rebuilt Athlone House, the $137 million home of Russian oligarch Mikhail Fridman. Replacing an equally hideous and ostentatious Schloss that had fallen into disrepair, this new, huge, Dutch-gabled monstrosity stands on the high ground off Hampstead Lane, with a proud outlook over the Heath. The case for sanctions and confiscation of Fridman’s assets is still ongoing.

Up until a couple of years ago, things were very different, with blue-chip bankers and top-notch lawyers lining up to help launder Russian money. Every level of society kowtowed to the ruble. A great-grandson of the former prime minister H. H. Asquith, Raymond Asquith, the third Earl of Oxford and Asquith, who was M.I.6’s station chief in Moscow in the 1980s, has spent the last two decades working for Dmytro Firtash, a Ukraine-born gas billionaire and associate of Vladimir Putin’s, regarded by the United States as having “links to organized crime.” Baron Barker of Battle, who sits in the House of Lords, has jumped into bed with all manner of oligarchs, and for some time was executive chairman of an energy company owned by Oleg Deripaska, once the richest man in Russia, now on the United States’ sanctions list.

And it wasn’t just well-born mandarins lining their pockets. I spent much of 2013 and 2014 working as a personal tutor for Russians, shuttling between homes in Regent’s Park and Cap d’Antibes. I even wrote essays for an oligarch’s son, who was studying at a London university. I was somewhat bemused to see his father—who was always perfectly nice to me—appear on the Treasury Department sanctions list in 2018.

Momentarily airborne, you can see your flying reflection for a suspended moment before complete immersion. An abrupt wake-me-up to set the day straight. Half the men’s changing area used to be divided by a modesty screen to accommodate nude sunbathing. Much to the gay community’s dismay, it’s been removed.

On one of the last summerish days this month, I walked past the Bird Sanctuary Pond, where the no swimming signs are blissfully ignored when the mercury hits 90 degrees and where crowds of teenagers vape and gossip along the path. Women shuttled past me, to and from the Ladies’ Pond, and the promise of one last evening for the many different tribes of Londoners who treasure the Heath hung in the air.

On a bench overlooking the Men’s Pond, Gordon Slade, an avuncular gay man in his 50s, told me how he moved to the area to be close to the Heath. He said he’d never seen anyone go into, or come out of, the Russian compound. But he was more perturbed by the recent ban the local council had placed on nude sunbathing on the Heath. Some have nothing to hide. Others have everything.

Charlie Baker is the editor of The Fence magazine