The Hard Rock Cafe (no drugs or nukes) is on the ground floor of a strange building, tall and thin with a huge mint-striped segmental pediment at the top. It was built by Collcutt & Hamp in 1907.
The pediment is broken by a pylon supported by a muscular Atlas, who has been cast in several bits so the joints make him look a bit like Action Man with swivelling torso and legs.
The fourth floor has a mystery coat of arms on it, which were kindly identified for me by Rouge Dragon Pursuivant at the College of Arms as the arms of Gloucester.
It turns out that the building is on the site of Gloucester House, home of Prince William Frederick, Duke of Gloucester in the 19th century. Despite being Chancellor of Cambridge University he was known as Silly Billy.
However, the arms are not those of the Prince but of the City, according to Rouge Dragon Pursuivant: "Dukes of Gloucester do not, of course, have any real connection with that city, and the appropriate way of commemorating the fact that this one lived there would really be to have shown his personal arms (a version of the Royal arms). It is possible they did not obtain permission for this in 1907, or simply mistakenly thought that ‘Gloucester House’ had had some connection with Gloucester."
The monogram on the pylon is a bit of a mystery - it could be JDJ or DJJ or even JJD. The ground floor was originally a motor showroom apparently, so perhaps the initials stand for an early make of horseless carriage.
The block's current owner is Sir Alan Sugar. The hire'em and fire'em entrepreneur went into property a number of years back, buying the Hard Rock Block and converting the top floors into enormous and very pricey flats. The front ones have lovely views over Green Park.