In the early 21st century, some houses are being reconverted to residential use, because offices in old houses are no longer as desirable as they were in the post-war decades, while the number of super-rich in London is at a high level not seen since at least 1939. The average house price in Belgravia, as of March 2010, was £6.6 million, although many houses in Belgravia are among the most expensive anywhere in the world, costing up to £100 million, £4,671 per square foot (£50,000 per m2).