Once you've built the Batcave, actually living in it becomes ordinary.
In the quiet hills of Hampstead, a fortune built on human longing — the desire to connect — has been poured into stone, steel, and shadow. Sergey Frolovichev, who helped build two of the world's largest dating platforms, spent five years and £15 million reimagining a 1934 Georgian mansion as a private mythology, complete with a hidden underground lair inspired by a fictional vigilante. Now, drawn toward a simpler life in Italy, he offers the unfinished dream to whoever can afford to inherit it — a reminder that even the grandest personal visions are, in the end, transferable.
- A billionaire's five-year obsession with Batman has produced one of London's most extraordinary — and unfinished — properties, now suddenly on the market for £29.95 million.
- The mansion's underground Batcave, with its retracting floorboards, hidden staircases, and pool-turned-dancefloor, represents a level of personal fantasy rarely seen in residential real estate.
- The tension lies in the incompleteness: the bones are exceptional, but the interior remains raw 'shell and core,' meaning the buyer inherits both the vision and the burden of finishing it.
- Agents at Draper London believe the right buyer could push the sale price £5–7 million above asking, with a fully finished property potentially worth £40 million or more.
- Frolovichev has already moved on — choosing Italy and family life over the Hampstead fortress — leaving the market to decide what a billionaire's abandoned dream is worth.
Sergey Frolovichev built his wealth connecting strangers — first through Badoo, then Bumble, which sold to Blackstone for $3 billion in 2019. What he chose to do with that wealth was more personal: he bought a 1934 neo-Georgian mansion on Greenaway Gardens in Hampstead for £13.5 million and spent the next five years and another £15 million turning it into something closer to a private mythology.
The house is formidable on its own terms — 14,501 square feet, seven bedrooms, six reception rooms, a health spa, steam room, sauna, cocktail bar, and a main bedroom that spans the full width of the building and opens onto two private roof terraces. A triple-height entrance hall greets you at the door. Staff quarters sit on the lower-ground floor.
But the true ambition lives below. Frolovichev became consumed by Christopher Nolan's Batman films and resolved to build his own Batcave beneath the property. A set of retracting floorboards conceals the staircase down. The corridor below is lined with display cabinets. The main chamber was designed as a studio or workshop, though the fantasy seems to have been the point all along. Hidden caves branch off throughout. A car stacker stands ready. The swimming pool can be drained and converted into a dancefloor.
All the infrastructure is in place — underfloor heating, full wiring, mechanical ventilation, even a private well in the garden. But Frolovichev stopped before the finishing work was done. The mansion sits in 'shell and core' condition: structurally complete, systemically ready, but interior-bare. He has chosen to relocate to Italy with his wife and children.
The asking price is £29.95 million. Agents at Draper London expect it to sell for £5–7 million above that, and estimate a fully completed property would be worth at least £40 million. The buyer will need more than money — they will need more than a year to finish what someone else imagined. As the listing agent put it, this is a once-in-a-generation chance to complete one of Hampstead's finest homes. What goes unsaid is simpler: someone else will have to finish the billionaire's dream.
Sergey Frolovichev made his fortune in the world of dating apps—first Badoo, then Bumble, which sold to the American investment firm Blackstone for $3 billion in 2019. Now he is stepping away from one of his most ambitious personal projects: a £30 million mansion in Hampstead, north London, that he has spent the last five years transforming into something between a billionaire's playground and a film set.
The house itself is substantial enough. Built in 1934 in the neo-Georgian style, it sits on Greenaway Gardens and spans 14,501 square feet inside, with another 7,921 square feet of external terraces. Frolovichev bought it for £13.5 million and then committed £15 million to its renovation—a figure that speaks to the scale of what he was attempting. Seven bedrooms, six reception rooms, a media room, games room, health spa, steam room, and sauna. The main bedroom runs the full width of the house and opens onto two private roof terraces. Everything is ensuite. There is a staff studio on the lower-ground floor. A triple-height entrance hall. A cocktail bar in the games room.
But the real obsession lives underground. Frolovichev became fixated on Christopher Nolan's Batman films, particularly Christian Bale's portrayal of the vigilante, and decided to build his own version of the Batcave beneath his home. The entrance is hidden behind a set of retracting floorboards that conceal a staircase. Once you descend, you walk through a corridor lined with display cabinets before reaching the main chamber—designed as a studio or workshop, though the actual purpose seems more about the fantasy itself. There are hidden caves throughout. A car stacker waits to hold your vehicles. The swimming pool can be drained entirely and transformed into a dancefloor.
The house is fully plumbed, wired, and heated with underfloor heating and mechanical ventilation. It even has its own well in the back garden. But here is where the story shifts: Frolovichev has stopped the work. The mansion remains in what the real estate industry calls "shell and core" condition—the bones are there, the systems are in place, but the interior finishing is incomplete. He has decided to move to Italy with his wife and two children instead.
The asking price is £29.95 million. The agents at Draper London believe it could sell for £5 million to £7 million above that figure. The buyer will inherit not just an unfinished mansion but the responsibility of completing it—a process that could take more than a year. Once finished, the agents estimate the property will be worth at least £40 million. Craig Draper, speaking for the firm, called it "a once in a generation opportunity to create one of the finest new residences in Hampstead." What he meant was: someone else will have to finish the billionaire's dream.
Notable Quotes
This sale offers a once in a generation opportunity to create one of the finest new residences in Hampstead.— Craig Draper, Draper London
The Hearth Conversation Another angle on the story
Why would someone spend fifteen million pounds on a basement and then just... leave?
Because the fantasy was the point, not the living. Once you've built the Batcave, actually living in it becomes ordinary.
But he's selling it. Doesn't that mean he failed?
Not failed—moved on. He made his money. He built the thing. Now he wants to be in Italy with his family instead of overseeing contractors in Hampstead.
The buyer has to finish it themselves?
Yes. They're buying the skeleton and the obsession. The real cost is in the completion.
Do you think anyone will actually use the pool-dancefloor?
Someone will. But probably not the way he imagined it.
What does a Batman-themed basement say about a person?
That they have enough money to build whatever they want, and enough imagination to want something strange. That's rarer than you'd think.
Will it sell for forty million?
If the buyer is the right kind of person—yes. If they're just looking for a house, no.