Porter gives several (non-silicon) examples, including the wine-growing industry in northern California and the flower-growing business in the Netherlands.

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The Netherlands would not be the natural first choice for anyone starting a flower-growing business today were it not for the fact that the business is already there.

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There are herbs growing in flower boxes at the bus stop, raspberry canes on waste land, cabbages in the flower beds at the local park - and even beans between the graves in the local cemetery.

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The flower had been thought to be extinct but was found by chance growing in Yorkshire in the 1930s.

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The next Challenge, which kicked off last week, is tackling urban agriculture, a radical approach to growing our food inside our cities (think more skyscraper farms than flower box herb gardens, although the project will address both).

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