Beneath an anonymous back street in south London lies a vast underground air-raid shelter that has been turned into a pioneering urban farm supplying supermarkets and restaurants in the capital.
The World War II shelter in Clapham, which could protect up to 8,000 people from Nazi bombs, consists of two large tunnels that were intended to one day become an extension of the London Underground.
That never happened and the shelter lay abandoned for 70 years until two entrepreneurs, Steven Dring and Richard Ballard, decided to grow broccoli, coriander, fennel and a host of other vegetables as so-called micro leaves, also known as micro herbs, grown from seedlings but harvested early when the first leaves form.
"We need to create these new fertile spaces" to meet increased demand from a growing global population, Dring told AFP on a visit to the "Growing Underground" site—some 33 metres (108 feet) below street level.
The vegetables are grown with hydroponics, using nutrient solutions in a water solvent instead of soil.
The technique can also be used to grow a wide range of produce including tomatoes and baby peppers, Dring said.
"We predominantly grow micro herbs, which are standard herbs, from different seeds."
"But what we do is we grow them to a very small stage, before the first true leaves start to come out," Dring said.
The micro herb broccoli takes between three and five days to grow before being packaged up in the shelter and sent off.
Experts say vertical and urban farming could be ways not only of facing up to population growth but also growing urbanisation worldwide as well as climate change.
Nottingham University's Centre for Urban Agriculture said on its website that urban farms create jobs, reduce transport costs and pollution as well as offering an "opportunity to develop technologies".
The "Growing Underground" project sends its data on humidity, temperature and plant growth to Cambridge University to try and improve efficiency.
"What these guys are doing is modelling for us which one is the optimum environment for each product," Dring said.