They have panoramic views, iris recognition in the lifts, and a 24-hour concierge who will stock the fridge with champagne or charter a private jet.
But as the rest of the nation upgrades to fibre-optic broadband, London's most expensive apartments have been left in the digital dark ages, stranded at the end of often painfully slow copper lines.
Only the most wealthy can afford a pied-à-terre at the One Hyde Park development opposite Harrods, in Knightsbridge, but it seems even the average £22m price tag is not enough to buy a superfast internet connection. The flats went on sale just three years ago, but their broadband speed is well below the national average.
The problem is not confined to Knightsbridge. BT is spending £2.5bn wiring up 19m homes with faster internet, with the government bent on ensuring broadband reaches rural locations, but as the country's most far-reaching infrastructure project nears completion, it has emerged that many of the most exclusive addresses in London and other big cities are being overlooked.
Across the capital, and particularly along the banks of the Thames, where luxury steel and glass high-rises now jostle for space, mining tycoons, investment bankers, rock stars and footballers spend many precious minutes in front of buffering screens when trying to make a Skype call or watch films over the internet.
One Hyde Park has a top speed of around 10 megabits per second – well below the 18Mbps national average. The building's developer, Candy & Candy, says it is now negotiating with BT to install a 100Mbps service.
Multi-unit dwellings, be they council tower blocks or high-end developments, often have a dedicated line running from the ground floor to the nearest telephone exchange. These lines are made of copper, and can run long distances, slowing the speed at which information travels.
BT's upgrade project is replacing copper wiring between the exchange and the green cabinets found on most streets. But it cannot help properties such as Pan Peninsula, the Canary Wharf tower that claims to hold London's highest private apartments, or Arlington Street, the Candy brothers' development around the corner from Piccadilly, because they are not connected to a cabinet.
"Internet today is a bit like having water or electricity," said hedge fund manager Radenko Milakovic. His London base is just down the road from near One Hyde Park at a development called The Knightsbridge, where the largest properties sell for £14m, but until recently the top broadband speed was 8Mbps.
"One should have access to the best infrastructure, particularly if you are in central London, whether you are in Brick Lane or Knightsbridge. Fast, uninterrupted and reliable internet should be available to everyone."
Milakovic has a back-up server in Bulgaria, which constantly updates the data he gathers in London. On the BT line, the process of copying each new file would have to take place overnight to avoid jamming the service during the daytime. Downloading films was just too slow to contemplate.
The problem has left a gap in the market and Hyperoptic, the niche operator that last year raised £50m from financier George Soros to fund its expansion, has begun wiring up buildings across town. Such is the appetite for the internet that Hyperoptic has now signed up 150 London buildings, housing 35,000 flats, and is expanding to other big cities in the UK.
It targets larger buildings, from affordable housing in the former Olympic Village to posher places such as The Knightsbridge, where Milakovic can now download large files in seconds and back up his server throughout the day.
BT's top speed for retail, as opposed to business customers, is up to 300Mbps, while Hyperoptic can run up to 1 gigabit (equal to about 1000 megabits) per second. Both are more than the average family needs, but they allow media to flow into the home at an unprecedented rate.
Thinkbroadband editor Andrew Ferguson said: "Developers are starting to see a broadband impact on rental and resale prices. It's not just about having a Jacuzzi."
Harvey Wolfinger's business, Invernetwork, counsels advertisers on how to spend their money with Google. He lives at the Norman Foster-designed Albion Riverside in Battersea and before Hyperoptic wired his building 18 months ago, the typical speed was a paltry 1.5Mbps.
"We complained endlessly to BT, but they said we were too far from the exchange," he said. Downloading advertising videos could take 20 minutes, while watching BBC catch-up programmes on the Sky Plus box was simply not possible. At Wolfinger's home in Scotland, where the internet came courtesy of a satellite service, the connection was many times faster at 20Mbps.
"In real terms we were better off in the Highlands of Scotland, in the remote munros, than we were in London."
The solution for larger buildings is to replace the copper with a fibre line from the exchange to the premises – or FTTP – but BT is in no rush to do this. It has installed FTTP in some places, for example Chelsea Bridge Wharf in London and the Big Peg and King Edward's Wharf in Birmingham. But its real focus is on upgrading cabinets – FTTC – a system which arguably delivers more bang per buck.
A BT spokeswoman said: "The presence of exchange-only lines can limit our options for delivering fibre but we work hard to deliver a fibre-based solution to such premises where we can. The vast majority of our rollout is FTTC. The technology enables us to deliver high-speed fibre broadband to the widest possible footprint much more rapidly and cost-effectively than would otherwise be possible using FTTP."
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