The Slow Food Movement is something Robin and Ikuko identify with but, in what appears to be a signature individualistic way, don’t subscribe to. Plants grown slowly outdoors, Robin says, have to adapt to more environmental changes than those nurtured in a greenhouse. The terpenoid metabolites and phytoalexins that the plants produce in order to fight stress, also serve to increase their nutritional value and flavour far beyond those of well-watered, nitrogen-pumped greenhouse crops.

‘People say, ‘should I buy organic?’’ says Robin, ‘and I say, ‘only if it’s fresh’.

The importance of freshness and provenance is underrated.’ In terms of flavour, nutrition and the knock-on carbon impact of imported goods, he says, ‘You’re better off buying something from just down the road.’

‘The first deliveries that we did,’ says Robin, ‘[our customers] weren’t so much amazed that Japanese produce could grow in England, it was that they had never seen fresh leaves with dew still on them, crisp and firm. When I was a child, my mother had a massive garden and she grew most of our stuff in there, so I had vegetables that were just harvested. To give other people the chance to taste something that is just a few hours old is one of our key selling points.’

On the way out of the greenhouse, Robin shows me their baby Sansho pepper trees that grow spicy leaves and berries similar to Szechuan peppercorns. I join the team for tea from thermoses in the hot sun. We rest on a pallet and there is little chatter apart from my own with Robin, who says that Brexit looks positive for growers like him.

‘For me, leaving Europe is great because the pound will fall and imports will be more expensive,’ says Robin. He tells me that due to the quirks of the system, NamaYasai do not get the subsidies that bigger farmers and social enterprises benefit from, and he hopes the post-Brexit economy will encourage more people to give local farmers their custom.

Taking the dregs of our tea with us, Robin addresses his team and takes some of us up narrow wooden steps beneath an oak tree laden with acorns to the Chicory Field. It’s so-named after the blue-flowering chicory plants that spring up each year, used as green manure when the farm was first located here. Robin and Ikuko have more land than they are currently using, but their big plans over the next year include the construction of a second large glasshouse.

Their business has grown well from early days, supplying by the barrow at boot fairs, then at farmer’s markets. Still, they have much to discover, says Robin. ‘No farmer stops learning.’

The Chicory Field is notable for its absence of polytunnels and the abundance of weeds and flowering plants – all of them profitable in different ways, like the nasturtiums that find their way into salads. Robin shows new recruits how to pick out cash crops from weeds – ‘nature doesn’t plant in neat rows’ – and to pull them out, laying the weeds in tidy bundles at the base of the plants as mulch.

‘Taste, nutrition and freshness are paramount to what we do,’ says Robin. Their crops are harvested under torchlight, because – like workers on a return commute – plants look tired and dehydrated at the end of the day. ‘The same crop at 4am looks lush, firm, full of moisture,’ says Robin. ‘Somebody here once said they had never eaten salad or vegetables without dressing on, he was amazed that we just ate the stuff as it was. Yet, if it’s grown outside, it’s fresh and not had sprays of any sort, then you get these superb flavours.’

This attention to detail has attracted NamaYasai a number of high-calibre regular customers, such as The Ledbury, Umu and Flat Three in London. Many chefs like to work closely with the farm and base their menus on what is seasonally available. London’s Koya Bar visit regularly, to work on the farm and harvest ‘anything special’ that they find. ‘The restaurants need to be continually innovating and doing new things to try and stay ahead,’ says Ikuko, who meets us after my tour.

‘There’s a new generation of chefs that don’t stick to one tradition. French, Italian; it’s all fusion and very creative… [their restaurants] tend to be independent and smallish in size, so they have more discretion in what to cook.’ Ikuko and Robin learnt early on that their growing methods aren’t best suited to big chains that require board meetings to tweak a menu.

What they are agreeable to, however, are chefs with a taste for adventure and variety. NamaYasai grows five different beetroots: white, candy, golden, crapaudine and English. Add to these currant tomatoes, Hamburg parsley – of which you eat the root – Tokyo turnips, mizuna, quince, mulberry, crab apples, plums, Asian pears and Japanese cherry flowers, edamame and Shishito peppers, to name a few. I ask what their favourite ingredients are, and Ikuko says daikon is the most versatile.

‘You can do anything [with daikon],’ she says. ‘Raw, casserole, stew, even make pancake-type things. My cooking starts with ‘what do I have to do with all the leftovers and rejects?’ rather than what do I want to cook, and daikon is the easiest to think about. On the other hand, the best thing for me is the aubergine; it’s very different from the aubergine you buy at the supermarket. As you cook the flesh, it almost melts.’

I wonder whether Robin and Ikuko find that customers are becoming more savvy and adventurous buyers. ‘People might be interested in fancy food,’ says Ikuko, ‘but not necessarily eating as a habit.’

‘They don’t appreciate the value of food,’ adds Robin. ‘That’s why we encourage people to visit here. If more people knew what was involved with growing and harvesting, they would appreciate the value more, but price still rules.’

Like many small growers, NamaYasai operates on passion and hard work, not big bucks, but I get a sense that Robin and Ikuko wouldn’t be happier, or suitably challenged, doing anything else. ‘It is hugely enjoyable to work under the sun, to use your body and work physically,’ says Robin. While Ikuko, a graduate in soil science, says, ‘I can understand when I read something what it means, but actual growing? Nothing compares to the experience.’