There are an estimated 87 square miles of flat roofs in the capital and the Government wants enterprises to follow Germany's example of planting grasses and alpine plants on them. There could be council tax benefits for those that do.

The Barclays Bank building at Canary Wharf has already adopted the idea, as have a number of supermarkets. Green roofs help insulate buildings, cut flooding and provide a habitat for wildlife.

Housing minister Yvette Cooper told This Is Money:

"We need to develop the technology to support our Victorian terraces and Sixties tower blocks as well as our new homes."