News: two British entrepreneurs are constructing a hydroponic farm in a network of tunnels under south London that could supply local restaurants and retailers with fresh herbs and vegetables.

Richard Ballard and Steven Dring's Growing Underground project is located in tunnels beneath the London Underground's Northern Line that were originally built as air-raid shelters during the Second World War.

Intent on demonstrating that it is possible to operate a commercial urban farm with a minimal carbon footprint, the entrepreneurs plan to transform 2.5 hectares of the disused air-raid shelter into growing space that will supply produce to London businesses, reducing the amount of food miles "from farm to floor".

Ballard and Dring collaborated with horticulturalist Chris Nelson to develop a hydroponic system that makes the most of conditions in the tunnels and enables them to grow a variety of micro herbs, shoots, miniature vegetables and other foods.

The hydroponic farming method involves growing plants in a mineral-rich solution on specially constructed growing platforms under controlled temperature and lighting conditions.

The farm's subterranean location means that the farmers don't need to worry about pests and diseases, or Britain's unpredictable weather.

After spending the past 18 months conducting growing trials in the tunnels, the entrepreneurs have launched a crowdfunding campaign that aims to raise £300,000 to support the business' expansion.

"Integrating farming into the urban environment makes a huge amount of sense and we’re delighted that we’re going to make it a reality," said Richard Ballard. "There is no 'could', 'might' or 'maybe' about our underground farm. We will be up and running and will be supplying produce later this year."

The farm's carbon neutral credentials are achieved by utilising low energy LED grow lights, locally sourced green energy, a recirculating water system and the 33 metres of earth above the tunnels, which helps maintain a consistent temperature.

Growing Underground has received backing from celebrity chef Michel Roux Jr, who lives close to the farm's entrance near Clapham North station.

"When I first met these guys I thought they were absolutely crazy," said Michel Roux Jr. "But when I visited the tunnels and sampled the delicious produce they are already growing down there I was blown away. The market for this produce is huge."

The first crops grown at the farm will include pea shoots, rocket, mizuna, broccoli, red vein sorrel, garlic chives and mustard leaf, as well as edible flowers and miniature vegetables. Following further development it will become possible to grow crops including mushrooms and heritage tomato varieties.

Full-scale farming is set to commence in March, with the first produce expected to be available in late summer.

Meanwhile plans are have recently been unveiled in Paris to convert the city's disused Metro stations into swimming pools, theatres and galleries.