LONDON • World War II is long over, but the fight to feed the world is still being fought.

There is good news from one "battle front". Under an anonymous back street in south London lies a vast underground air-raid shelter that has been redesigned as an 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 German bombs, consists of two large tunnels that were intended to one day become an extension of the London Underground train network.

That never happened and the shelter lay abandoned for 70 years until entrepreneurs Steven Dring and Richard Ballard decided to repurpose them.

Now, they grow broccoli, coriander, fennel and other vegetables as so-called micro leaves that are harvested when the first leaves form.

"We need to create these new fertile spaces" to meet increased demand from a growing population, Mr Dring said at the Growing Underground site 33m below the road.

Staff wear protective clothing and there is a strong smell of vegetables and humidity in the shelter.

The vegetables are grown with hydroponics, using nutrient solutions in a water solvent instead of soil.

The only other ingredient required is light. The tunnels are illuminated with pink LED lights, giving them a futuristic look.

The micro herb broccoli takes between three and five days to grow before being packaged in the shelter and sent off.

Fans enthuse about the intensity of the flavours of the produce.

Customers include Marks and Spencer, which offers the produce in some of its supermarkets, several stalls at London's Borough Market and many restaurants - helped by the patronage of celebrity chef Michel Roux Jr of Le Gavroche.

Mr Dring and Mr Ballard latched onto the concept of vertical farming - producing food in vertically stacked layers - which was developed by US biologist Dickson Despommier in his 2010 book.

Their request to use the shelter in Clapham was eagerly taken up by the owners of the space, London's public transport company. This type of farming is "100 times cheaper" than setting up an urban farm on the surface, Mr Dring said.

Their customers are happy with the result. "I think the story is fantastic," said Mr Charlie Curtis, an agronomist at Marks and Spencer supermarket.

AGENCE FRANCE-PRESSE