these herbs and salad are growing in an underground World War Two air raid shelter.

The zero-carbon vertical farm offers a glimpse into how farms could look in the future.

"Growing Underground is the first farm for Zero Carbon Farms and what we do here is we sustainably grow fresh produce in former World War Two air raid shelters."

Agricultural tech company Zero Carbon Farms grows plants in Clapham, south London.

The densely populated area has no room for conventional agriculture.

But 100 feet below ground there is over half a mile of tunnels, and technology has made farming here a reality.

Olivia O'Brien is the business development director at Zero Carbon Farms.

''We grow this both for the fresh produce industry and also the extraction market. And the way that we do it is we use renewable energy, we use recirculating water, and we're able to grow the crops 365 days a year with little impact on the environment.''

The farm's subterranean location keeps it insulated from the cold.

That ensures steady growing conditions year-round.

Instead of soil, seeds are sowed on carpet offcuts.

Zero Carbon Farms says farming here uses 70-90% less water and 95% less fertilizer than typical agriculture.

Their fresh produce can appear on a diner's plate within two hours of harvest - producing minimal emissions on the journey to get there.

"Their yields and their efficiencies of their growing times are as optimized as possible. And that also means that you get incredibly nutritious, very, very tasty crops that, you know, have a very long shelf life. So you get less food waste because of things like that.''

Vertical farming is a fast-growing industry with billions of dollars being pumped into projects across the globe.

It's seen as a part of the solution to the food security challenge posed by population expansion

at a time when climate change and geopolitics threaten supply.

''Qe ultimately need to develop more ways of growing more food to feed the world. And we don't have more farm space to do it and we don't have another planet to do it on. So we essentially have to develop alternative, and not methods that are going to replace traditional farming, but really methods that are going to support traditional farming in producing more food for the world.''

Zero Carbon Farms plans to double its growing space in 2023,

responding to strong demand for its peashoots, rocket and watercress from major British retailers like Marks &

Spencer local restaurants.

The farm's head grower, Tommaso Vermeir, is excited for the industry's future.

''You know, the future is very, very bright for this industry. I think that what really is kind of going to be the pivotal or a fundamental pivot point is the right application of technology as well as, you know, a broader kind of a broader range of research into different cultivation styles, different parameter controls. And yeah, I mean, I'm very excited. I'm looking forward to it.''