Of the dozens of apartments that have sold there, only a handful are registered in the names of actual people. The rest are held in the names of corporations.
And most of the apartments, which belong to Arab sheikhs, Russian oligarchs, and other secretive billionaires, are not even considered primary residences. The place has been called a "ghost town" and is pitch black at night.
Vanity Fair's Nicholas Shaxson recently wrote a great feature about the building and its shadowy residents. While he had a hard time finding out about many of the owners, and could not even get inside the building, Shaxson reported some crazy tidbits about One Hyde Park.
Even for the world's most expensive apartment building, the security is extreme. Shaxson writes:
In fact, the emphasis everywhere is on secrecy and security, provided by advanced-technology panic rooms, bulletproof glass, and bowler-hatted guards trained by British Special Forces. Inhabitants’ mail is X-rayed before being delivered.
There are also slanted vertical slats on all the windows to prevent people from peering in.
For a place where barely anyone lives full-time, that's a lot of security.