What does it mean? Well, essentially, in cities where development sites are scarce, it’s about how to exploit the space above existing infrastructure hubs to build major schemes. A current example is the new Deutsche Bank HQ being created by Landsec above Moorgate station in London.

To be fair, it’s not an entirely new concept: London alone has seen schemes built above Charing Cross and Cannon Street stations and, of course, back in the 1980s, the Broadgate development around Liverpool Street station led the way in terms of taking advantage of the big footprint – and space above – major transport hubs.

However, the approval of a recent planning application to build ‘under’ is possibly a more interesting sign of things to come.  Westminster council has given the green light for Reef Group’s plans to redevelop the four-storey underground car park under Cavendish Square into a 280,000 sq ft West End retail and leisure complex.

Of course, building underground brings its own logistical problems but this scheme does make you start thinking about the other subterranean spaces around the capital which could have potential. Car parks are, of course, the prime candidates especially as the need for private parking dwindles in the face of the congestion charge and clean air measures. We’ve already seen some of the ‘last mile’ distributors start to repurpose underground car parks as distribution hubs and the trend is likely to continue.

It seems that the future of urban development could lie partly up in the sky but also underground.