Where Hampstead Heath meets Highgate Hill, behind steep red-brick walls, there is a garden. In the garden, hidden by a protective coppice of tall trees, there is a house. If we were to step through the heavily boarded gates, edge past the 24-hour security, and through those trees, we'd find the shell of a mansion on whose lawns George VI played tennis; in the 1940s Princesses Elizabeth and Margaret sipped tea on the parterre. Witanhurst is the second largest private residence in London, narrowly beaten by Buckingham Palace. Currently undergoing a £50m redevelopment, the 95,000 sq ft property, when finished, will boast 25 bedrooms, 12 bathrooms, a cavernous underground leisure complex including a 70ft swimming pool and two-tiered cinema, all set within five-and-a-half acres of ornamental gardens.

The Highgate Society – a residents' association – is campaigning against the project, and the size and scale of the works seems out of place in an area of London that has always felt more like a village. There is a problem facing protesters, though: nobody is quite sure who owns the building. The story of Witanhurst is emblematic of the obfuscation and skulduggery surrounding high-end property in London, a city whose housing market has become the asset class of choice for the world's skittish billionaires.

Witanhurst had fallen into a state of crumbling disrepair under the ownership of an absentee Middle Eastern family when it was bought by property developer Marcus Cooper for £32m in 2007. Cooper almost immediately put the place back on the market for £75m, finally accepting £50m in 2008. The purchaser was a British Virgin Islands-based entity, Safran Holdings, the vehicle for anonymous eastern European buyers. Plans were filed for the Babylonian excesses currently nearing completion in N6. Cranes went up, massive lorries started chuntering around the heath, a vast orangery began to poke its dome above the treetops. But still the owners remain hidden behind their labyrinthine tax-avoidance schemes. Apparently not even Robert Adam, the architect in charge of the project, knows his clients' identity, with all negotiations handled by intermediaries and advisers. For all the internet speculation – there is a section devoted to Witanhurst on David Icke's website – we are no closer to knowing the owners of this most elephantine of white elephants.

Witanhurst is an extreme example of the way overseas money is radically altering London's landscape – both its physical appearance and the shape and structure of the lives of everyday people. The inflation of the property market has unmoored the city from the rest of the country, with a combination of rampant speculation and a lack of supply pushing valuations into the stratosphere. Already in the capital's swankier boroughs – Kensington and Chelsea and Westminster – average prices have broken through the £1m mark, with Camden, Hammersmith and Fulham and the City not far behind.

In 2013, 85% of new houses in London were sold to non-UK buyers, with investors from east Asia driving demand. Foreign money dominates the top end of the market, with almost half of all homes over £1m bought by non-UK residents. Investors flock to property shows in Moscow, Kuala Lumpur, Beijing and Singapore, snapping up houses off-plan, in cash. The majority of foreign investors either rent out the homes they purchase, or "buy to leave" – allowing the properties to stand empty and relying on the inexorable rise of the London market to deliver returns.

It was the resilience of house prices during the 2008 crash that lent London property its aura of gilt-edged invulnerability. Where once investors would have bought safe-haven assets like gold and bonds in times of turmoil, now they buy bricks and mortar. With Swiss banks – smarting after the financial crisis – less willing to fulfil their traditional role of no-questions-asked banking for the world's super-rich, London's high-end property has come to fill that gap in the market, cheered on by a grateful government. The luxury apartments of south-west London, the empty mansions of Notting Hill and Hampstead have become lavishly upholstered safety deposit boxes, stucco-fronted bank vaults.

Last weekend, I took a drive through the city at night. I came down Park Lane just after nine, edging around the Lamborghini Murciélagos parked up outside the Dorchester, then through the tree-hushed squares of Belgravia and into Knightsbridge. The rusty hulk of One Hyde Park, the Candy brothers' monolithic apartment block, lowered over me, every window black; I sidled past the Knightsbridge Apartments – a development favoured by Russians where pieds-à-terre go for £5m and up – and through Trevor Square to Brompton Road. I counted lit windows on the fingers of one hand. It was as if I was driving through some apocalyptic vision of a city snuffed of all life, of all light.

It is striking that in a recent survey of the UK's empty homes, Kensington and Chelsea sits alongside poverty-stricken boroughs in the north-west, with a 40% rise in unoccupied houses in the past year alone. Here, though, it is not a matter of economic destitution, rather that the international jet setters never intended to live in their gilded crash pads, or that their Embraers touch down so rarely that they have forgotten the names of their children, their wives' faces, their own many addresses.

London's itinerant billionaires are a private bunch, reluctant to open up their homes to the great unwashed. So I confect a detailed cover story – a wealthy godmother looking to relocate from Paris in the wake of François Hollande's punitive tax increases. The wealthy godmother exists; her putative immigration doesn't. Wrapped in this elaborate fiction (and a smart blazer), I set off into the world of London's super-prime property market: a world of private cinemas and helicopter pads, of panic rooms and indoor golf ranges, of oceanic swimming pools and underground tennis courts. A world of status, of power and, above all else, of money, of absurd, laughable amounts of money.

Address Kensington Palace Gardens, W8

Property 5-bed apartment

Size 5,000 sq ft

Outside space Small terrace, shared garden

Price £25m

The first Billionaire's Row I visit – two roads in London compete for the title – is Kensington Palace Gardens, often cited as the most expensive street in the world and home to Britain's richest man, Lakshmi Mittal. Also on this leafy stretch of W8 are the Sultan of Brunei, Roman Abramovich and, at an estimated £200m, the priciest house in the country, a mansion owned by music mogul Leonard Blavatnik. I edge past a sinister, gun-toting guard peering out from the gatehouse at the Notting Hill end of the street and make my way towards a modern block of flats sitting behind heavy iron railings.

Kensington Palace Gardens. Some of the most expensive homes in London – not to say the world – are to be found here. Photograph: Andrew Holt / Alamy/Alamy

It is a glorious spring day, frothy blossom falling from the cherry trees planted in the gardens of the Japanese ambassador's residence opposite. In front of the building, I meet the estate agent from Knight Frank – the leading seller of £5m-plus homes in the capital. He is unexpectedly charming. Not just the understandable charm of a man who'll make close to £1m in commission if I decide to purchase the apartment we're about to view at its full £25m asking price; instead there's something endearingly Glengarry Glen Ross about him, a tobacco-scented worldliness.

Kensington Palace Gardens was built on land owned by the Crown Estate in the middle of the 19th century, a mixture of hefty Italianate and Queen Anne mansions initially purchased by wealthy London merchants looking to escape the bustle of the city, gentry seeking royal proximity. Even at the time of building, houses on the street were thought too large for a single owner – a Mrs Murray of Maida Vale converted No 8 into two semi-detached villas, others remained unoccupied, with architects noting that the properties were "too large for the generality of families". Increasingly, the houses were turned into embassies and consulates, with the French, Israeli, Russian and Romanian embassies all taking up residence behind the stately avenue of plane trees that leads up the street's long incline. In 1937, number 12A was granted to the Nepalese for ambassadorial use in recognition of the Gurkhas' service to the British army.

It is only in recent years that private owners have begun to recolonise Kensington Palace Gardens. Roman Abramovich bought the former home of the Russian ambassador for £90m in 2011, spending countless millions more on a subterranean extension that will include a swimming pool and underground tennis court. Lakshmi Mittal liked the houses so much that he bought one for himself, spent a further £117m on a place for his son, Aditya, and then snapped up a run-down mansion for his daughter Vanisha for £70m in 2008. It is thought that the value of the three properties owned by the Mittal family on the street now tops £500m.

The influx of foreign capital into London's residential property market has led to an exodus of ambassadorial buildings away from luxury postcodes. The US embassy is moving from its current location in Mayfair's Grosvenor Square to the Nine Elms development across the river in Battersea. It is thought that the Chinese will soon join them, putting their vast Portland Place property up for sale. The Nepalese embassy – notable for its state of shabby disrepair – is likely to be sold for around £100m in the coming months, with staff relocating to more modest surroundings. It is a sign of the state of the London property market that even countries can't afford to keep up with the super-rich.

I am here to see a duplex flat on the ground and first floors of a sleek glass and steel building set back from the road. I'm ushered up marble steps, past a porter and into the apartment, where the vendor's representative, suited and simpering, welcomes us. We step into an anonymous vestibule, gloomy behind long net curtains despite the bright day outside. Shades of brown, burgundy, dark greens. The apartment has been in the same Middle Eastern family for decades, rarely used in recent years, and there is a sense as we walk inside that we are entering a museum, a time capsule whose very air was last breathed in the 1970s. We might be on the set of Argo. I ask if I can have a wander and, floorplans in hand, set off into the dark interior.

The walls of the drawing room are covered in silk toile, dotted with sombre quattrocento paintings of Florentine princes; a dark bronze sculpture of Pallas and the Centaur sits on the window ledge. Deep sofas slump beside coffee tables topped with silver-framed photographs of children in corduroy and velour. I wonder where they are, these bright-eyed youngsters now grown old. I walk to the eastern edge of the apartment where French doors give on to a large stone patio with empty troughs that must have once held flowers, fountains even. Communal lawns stretch away to high hedges, and if I lean out, I can see the red brick bulk of Kensington Palace.

"It may suit your godmother to have a place that is so…" the estate agent fishes for the right word "… of an era. It means she can update to suit her own tastes." He tells me of a Russian couple who paid £20m for a Kensington townhouse that was finished to an extraordinarily high standard, decided they didn't like the £150,000 kitchen, and so spent a further £1m ripping it out and putting in a new one. "Your godmother won't have that problem here," he says.

I make my way back inside, past a study with an enormous box-like fax machine, and into a mint-green kitchen filled with the fittings and fixtures of the early 1980s – an antique microwave, a rotisserie oven, stacks of formica and Bakelite. Beside the kitchen sits a small and sad-looking maid's room, a single 10p piece – one of the large, old ones – on the bedside table. Upstairs the four bedrooms have a vaguely nautical feel, as if they were luxury suites on an ocean liner. Bathrooms boast gleaming gold taps, deep baths, vintage cosmetics on display. I wander into the master suite's walk-in wardrobe, which is so vast – endless rows of mahogany – that I begin to think I'll never emerge. It is a relief to come back downstairs and out into the sunshine, leaving behind the sense of a world that has settled into a perpetual and hopeless gloom.

It is only later that I discover the dark history beneath the modernist block, its marble floors. The current apartment building was erected in the 1960s on the site of the London Cage, a wartime interrogation centre whose existence only came to light in 2005. On a site where apartments now sell for tens of millions of pounds, German prisoners were subjected to sleep deprivation, starvation, electric shocks and induced hypothermia. A rather sombre historical coda for the future inhabitants of this particular patch of Billionaire's Row.

Address The Bishops Avenue, N2

Property 7-bed house, 2-bed staff cottage

Size 21,000 sq ft

Outside space 0.75 acre

Price £40m

The next Billionaire's Row used to be known as Millionaire's Row, when having millions still marked you out from the crowd. The Bishops Avenue in East Finchley snakes northwards from Hampstead Heath, bisected by the rumbling A1. The first houses were constructed at the start of the last century by industrialists looking to build country houses within striking distance of London. George Sainsbury, son of the founder of the supermarket, was an early inhabitant, as was sugar baron William Park Lyle, who built Heath Hall, a 14-bedroom mansion, in 1910. In Evelyn Waugh's Scoop, the owner of the Daily Beast, Lord Copper, lives on The Bishops Avenue (in a clear case of life imitating art, Richard Desmond has two houses there now). As the road stretched northwards either side of the war, newer money moved in, with Billy Butlin and Gracie Fields building Hollywood-style mansions alongside Sir Peter Saunders and Katie Boyle.

Who would live in a house like this? The plush interior of a property on The Bishops Avenue. Photograph: Graeme Robertson

Then, at the end of the 1970s, overseas money arrived, a prophetic glimpse of the flood that would swamp London in the decades to come. The road is a kind of constellation of all the violence of the past 30 years, the nationalities of its residents a record of political and economic upheavals. Iranians arrived in the wake of the revolution and subsequent energy crisis. Cypriots came after Turkey invaded the island, among them Asil Nadir, the founder of Polly Peck (now a resident of HMP Belmarsh). On New Year's Eve 1984, fashion mogul Aristos Constantinou was assassinated by a mystery gunman in his home on the street. Saddam Hussein's occupation of Kuwait saw an influx of Saudis and Emiratis, with the Saudi royal family snapping up 10 of the street's 66 homes between 1989 and 1993. Finally, and with the greatest fanfare, the Russians, Indians and Chinese arrived.When Toprak Mansion, a vulgar neoclassical pile, was bought by Kazakh businesswoman Hourieh Peramaa for £50m in 2008, Mikhail Gorbachev was guest of honour at the housewarming party. Lakshmi Mittal, not content with buying up Kensington Palace Gardens, also has a house here.

More recently, stories about The Bishops Avenue have focused on the number of properties on the road that have been abandoned by their absentee owners, former palaces whose ballroom floors are slippery with guano, crunch with the skeletons of dead pigeons. The home Salman Rushdie bought and then converted into a safe house during the fatwa years is just one of those that now stands empty (in his memoir Joseph Anton, Rushdie misspells the name of the road throughout, referring to it as "The Bishop's Avenue"). A recent Guardian investigation found almost a third of the street's properties were empty, some abandoned for as long as 25 years. Edward Hollis, architectural historian and author of The Secret Lives of Buildings, describes the uncanniness of these deserted homes. "For many of these houses, the bricks and mortar has fallen to pieces, but the investment value remains the same, indeed has skyrocketed in recent years. There's something very surreal about these multimillion-pound ruins."

Another genial Knight Frank estate agent drives me up from Hampstead High Street, along the heath above Kenwood House, and left on to "The Bishops", as he calls it. As we drive, he tells me that the reports of empty properties on the road have been overstated, a stance echoed by Trevor Abrahmsohn, founder of luxury estate agent Glentree International. "On a street of 66 houses, it's perfectly normal for 10 or 12 to be uninhabited – and that's all we're talking about here. There are the Saudi properties, which were a bolthole from Saddam, there are two houses owned by a senator from Pakistan which were unfortunately repossessed [he's referring to former minister of privatisation, Waqar Ahmed Khan]. Otherwise, the properties that may appear to be vacant are all undergoing some form of regeneration.It's just that with the size of these projects and the complexity of planning permission, the gestation period from start to finish can be up to five years."

Faded grandeur: a collapsed ceiling at the Georgians on The Bishops Avenue, north London. Photograph: Graeme Robertson

Certainly, there is an air of industrial bustle as we make our way up the avenue. Barnet council has apparently refused to carry out any improvements to the surface of the road while so many of its houses are undergoing facelifts. There are dumptrucks and diggers, mini-loaders and bulldozers every 10 yards. I feel like I'm in one of my son's picture books. Finally, somewhat towards the wrong – A1 – end of the street, we pull through automatic gates and into a pristine turning circle of cream-coloured gravel. "This place has serious kerb appeal," the agent sighs, and I feel like I've dipped an icy toe into a world where people say things like this.

Stratheden, which is the rather och-aye official name, is better known as the Lego house, a gleaming crenellated lozenge in Cape Dutch style with a teal-green roof. In the entrance hall a Filipino maid greets us with a bow; behind her, modern art – something that looks Kandinsky-ish, a Keith Haring-esque sculpture on a plinth – blazes from every surface. The blond parquet steps down into an amaryllis-strewn drawing room: silver velvet sofas, a chaise longue with a bearskin throw slouched over it. We walk past a plush pink private cinema to a dining room whose tabletop is purple lacquer, beautiful silkscreen prints on the walls. It is from the kitchen, though, that you glimpse the house's main selling point. The garden stretches out dreamlike behind the house, espaliered fruit trees pushing forth their first sticky buds, a turquoise walkway with water flowing within and around it. At the bottom of the garden is an annexe – the entertainment room – whose roof is turfed with grass that seems almost blue in the sunlight. Beyond it, impossibly distant, a colonnaded staff cottage.

Descending from the main house into the basement, we pass an enormous bar whose 500-bottle wine rack is filled exclusively with mineral water – "Not to put off Muslim buyers," the agent explains – into a cavernous leisure complex. I look up and realise that we are walking beneath the turquoise water feature in the garden. Through it, high above, the sun hangs in the sky, a vision of a drowned world. We walk through the hushed air of the swimming pool, upon whose roof twinkle a galaxy of stars, a honey-coloured moon. Passing massage rooms, saunas, a service kitchen, we come up into the garden annexe which houses the 3,000 sq ft ballroom. Standing, slightly agoraphobic, in the centre of the sprung dancefloor, I look up to take in the most monstrous chandelier I've ever seen – tens of thousands of crystals dripping from a lake of gold.

The agent tells me that the house, like many on the street, had been bought by someone from the Middle East in the 80s and then stood more or less empty for 30 years. It was then purchased by a family trust who set about renovating it, hoping to turn a swift profit. It has been on the market since March last year.

Despite the garishness, the chandelier, the bad art, Stratheden has worked its magic upon me. I'm tempted to tell him that my godmother will take it. Then I remember that her move to London is a fiction, and worry that I've been spending too long in this world of the super-rich, and ask to be driven to the tube.

Address One Hyde Park, SW1

Property 3-bed apartment

Size 3,547 sq ft

Outside space Small balcony

Service charge £60,000 per annum

Price £16.95m

One Hyde Park, the Richard Rogers-designed monolith that sits at the junction of Sloane Street, Knightsbridge and Brompton Road, is London's most expensive apartment block. As with many buildings in the city, the money behind One Hyde Park is Qatari. The public face of the project may be the colourful Candy brothers (who also interior designed the apartments), but the financial clout is provided by former Qatari prime minister (and member of the ruling dynasty) Sheikh Hamad bin Jassim bin Jaber Al Thani. Along with Harrods across the road, the Shard, the Olympic Village, Chelsea Barracks and the US embassy on Grosvenor Square, One Hyde Park is part of a flotilla of properties owned by the small, gas-rich nation.

From the start, the building met with significant and sustained criticism. First, there was the question of quite how many of the flats had been sold, and to whom. An investigation by the Guardian discovered that 80% of the apartments had been purchased by offshore entities based in the British Virgin Islands, with ownership layered through sophisticated tax-avoidance schemes. The Observer revealed that only nine of 62 apartments were registered for council tax, with five of those nine paying the 50% reduced tariff for second homes. We know that at least one Brit lives in the building: Nick Candy owns a penthouse, where he lives with his wife, the Australian actor Holly Valance. Otherwise, the flavour is exclusively international. Sheik Hamad, via a Cayman-registered company, has a triplex on floors 11-13 of one of the block's four towers. Other residents are Rinat Akhmetov, Ukraine's richest man and a close ally of deposed former president Viktor Yanukovych. He bought one of the more expensive apartments for £136m. Also listed are a number of Kazakhs, including Vladimir Kim, a copper billionaire and former politician; Russians, among them Vladislav Doronin, who is stepping out with Naomi Campbell; Chinese, Malaysians and Nigerians.

For a historical perspective on the project, I turn again to Edward Hollis. "One Hyde Park plays an interesting double game," he tells me. "On the one hand it's there in Knightsbridge, right in the centre of everything, on the other it's a world set apart, a vertical gated community. It's built to exclude, like the grand houses of 14th-century Florence – those palazzos like fortified castles to store money." Hollis sees it as significant that One Hyde Park is a block of flats in a city more used to expensive houses. "In the 80s, the very wealthy would migrate to the suburbs, buying a huge place out by a golf course like General Pinochet. What's interesting about One Hyde Park is that it tries to imitate the density of New York. It makes the idea of owning a flat aspirational and this is a good thing: London needs to get denser, not bigger. It's such a spread-out city – it covers its own hinterland, there's no escape. If London keeps growing outwards, it will take over the rest of the country."

The view from an apartment at One Hyde Park, with Harrods illuminated in the distance. Photograph: View Pictures/REX

I arrive early for my meeting with yet another Knight Frank agent. I walk around the building's perimeter, smelling the freshly cut box hedges. The apartment block's four towers jut forward into the park like the prows of four enormous steam ships. Between each tower (I later learn that the Candys prefer you to call them "pavilions"), there is a lattice of glass and steel, ziggurats of shining staircases, glass lifts. The block is finned with slats of rust-coloured metal.

I go around to the front of the building – the Knightsbridge side – and browse the windows of the "retail units" on the ground floor that have been chosen to appeal to the apartments' residents, but also, one feels, to convey something about these residents to those of us on the outside, looking in. In the Rolex shop, a sales assistant stares narrowly at me. Next there is a showroom of sleek, gull-winged McLaren cars. Then a branch of the Abu Dhabi Islamic Bank, offering its Diamond Infinite Visa card. Daily ATM withdrawals are capped at £4,000.

I reach the entrance where a stocky, clean-shaven security guard eyes me suspiciously. After a brief and chillingly polite interrogation, the guard lets me through, and I make my way along a walkway that cuts through a low water feature where two black stone swans rise from the water, their necks intertwined. I walk into the high and shadowy reception area, where I meet the estate agent and a representative of Candy & Candy, a young blond woman with the clipped vowels and genial firmness of a Roedean hockey captain. She tells me that we'll take a tour of the building's communal areas before looking at the fourth-floor apartment I've come to inspect.

First stop is the library, which apparently attempts to replicate the atmosphere of a gentlemen's club. There are no books in the library. Even if there were, it would be too dark to read. Every surface is fashioned from dark wood, dark stone, the corners of the room are night-black. There are no other humans in the library. It's all a bit creepy. We make our way out into the reception and take a lift down into the basement.

There is a distinct smell of cabbage in the Serpentine Suite, a private dining room that sits between the golf simulator and the cinema, with its 18 comfy-looking seats and cashmere throws strewn casually over them. We make our way through to the sports facilities, where I'm asked to tie a pair of blue plastic bags over my trainers. A dark and silent swimming pool, ozone-treated "to avoid the smell of chlorine". The floor of the pool is of dimpled steel. Two saunas, two steam rooms, a squash court with digital scoring. All are empty. The sense of being the last subterranean survivors of some nuclear holocaust increases. The walls, the Candy rep tells me, are covered with eelskin. I press my fingers to the tacky material and draw back – there is something horrifying in these expanses of shimmering skin. Silence. We are deep under the Knightsbridge streets, but there is no rumble of traffic, no shudder of tube trains. Nothing but the gentle hum of air conditioning. Finally, as we are about to leave the leisure complex, I look up to glimpse a thin woman in pink Lycra, her jaw clenched, her body yoga-contorted.

With a quiet whoosh the glass lift carries us to the fourth floor. The apartment I'm being shown is on the city side of the building, its three bedrooms looking out towards Harvey Nichols. The interior is, again, dark, with a kind of light-eating quality to the long panels of wood. I am asked this time to remove my shoes – the rep slips off her leopard-print ballet pumps – and don fluffy towelling slippers as I make my way across the shagpile carpet. In the bedroom, she flicks a switch and a smoked mirror descends to hide the television. I feel like applauding. We make our way through to the wide drawing room, where curved sofas surround teak coffee tables. The windows – she taps one – are triple glazed, no sound breaks through the thick glass. The steel fins I'd seen from the outside block any potential view of one's neighbours.

A small, chrome kitchen nestles in one corner of the apartment, although the rep explains that most residents take advantage of the arrangement with the neighbouring Mandarin Oriental when they want to eat. There is an underground tunnel that runs between the two buildings, along which One Hyde Park's 85 serving staff will scurry with food from the hotel's Heston Blumenthal-run restaurant. I remove the slippers and we make our way back to the lift.

Again as I leave the building – the guard gives me another suspicious once-over – I'm hit by a sense of the deep melancholy that suffuses the world of the very rich, for all their money and luxury. The emptiness, the silence, that bookless and dreary library. It seems somehow fitting that each of the building's four penthouses has its own panic room. I wonder if the inhabitants of those sky-towers, those pinnacles of money, ever pause to wonder if it was all worth it? The feverish pursuit of privacy, the monomaniacal drive to avoid paying a penny of tax, the sense of being, as Hollis says, both in the city and somehow above it, all of this strikes me as terribly sad. It seems that, granted the riches of Croesus, all people really want to do is avoid other people.

I'll admit that part of my voyage into the world of the London super-rich has been driven by a kind of Through the Keyhole nosiness, a wish to feel that Daily Mail admixture of greed and envy that comes with the leather sofas and chandeliers, the cinemas and supercars. But that's not the whole story. Andrew Heywood, editor of Housing Finance International, describes the profound social repercussions of the "percolation effect", whereby shifts in prices at the top of the market trickle down to impact upon all other levels. This, he says, has permanently altered the shape of the city – for all its inhabitants. "Rich and poor can no longer live cheek by jowl," he says. "There is no longer the possibility of mobility across the city. If you get a job in west London, the only option is to commute. Now there is a cosmopolitan elite in central London, with the poorer inhabitants forced to move to the suburbs." He points out the wave of local boroughs selling their council housing stock – moves that have been described as "social cleansing". "In the end you'll get a divided city – it will lead to ghettoisation."

I also speak about foreign ownership of London property with Nicholas Shaxson, author of Treasure Islands, a brilliant and angry book about global tax avoidance. He is far from complimentary, describing it as "a rather grotesque demonstration of the UK's willingness to prostitute itself to the world's hot and dirty money… The UK has increasingly had cultural characteristics of a tax haven, notably the cowering subservience that successive governments have shown to flighty (and frequently very dirty) international capital. They want to attract it at all costs."

I think again of Edward Hollis's description of One Hyde Park as a vertical gated community, of the sinister guards at the gates of Kensington Palace Gardens, the soullessness of those empty streets and squares in Chelsea and Belgravia. A word that comes up again and again in the leather-bound brochures of these palatial homes is "exclusive", and that's exactly what they are. Either literally – through gates and guards – or metaphorically – through stripping an area of its character, its sense of community – the most striking effect of the colonisation of London by foreign investors has been the exclusion of everyday people, the erection of barriers, the destruction of social cohesion.

Now, as I drive past the blackened windows of super-prime London, past the privacy-finned triple glazing of One Hyde Park, I wonder how many of the rich are sitting there, in the darkness, looking out at us, at all the palpitating life of the city.

Alex Preston's third novel, In Love and War, will be published by Faber in July