It's the first hot day of spring, and on a sward in the gleaming Sussex countryside sits a big man in the thick woollen garb of the serious backwoodsman. He is Ray Mears, the celebrated survival expert and author of the forthcoming Ray Mears Goes Walkabout. And I, like many others, am a mad, mad fan.

His programmes regularly attract more than three million viewers, and his books, such as the recent Wild Food (and my favourite, the wipe-clean edition of Essential Bushcraft) have, over the past few years alone, sold a quarter of a million copies. And now he is celebrating the 25th birthday of Woodlore, the school of wilderness bushcraft that he set up as a young man.

My long-held admiration for Mears is such that I'm afraid he might be slightly scared of me when we meet in a woodland near his home. But of course it takes more than an obsessed fan to scare this seasoned adventurer - and when it comes to stalking he'd beat me hands down. Because Mears, don't forget, is as canny with a gun as he is with the beautiful artisanal knives he uses to carve flowers on to hand-turned wooden spoons.

Looking out over this stunning corner of wild Britain, Mears is quick to defend the farmers and gamekeepers to whom we nature-lovers owe so much. Take pheasant shoots, for example, which are criticised for burying thousands of birds each season.

“I've got no issue with the pheasant shooting. I've only been once - I don't like shotguns particularly, because they desensitise you. But the benefit it gives to the countryside is massive. It's the right sort of conservation. The cover you need encourages woodland and hedges. So many species benefit from it.”

And then there's the employment it brings to a beleaguered farming community. “Farming has almost ceased to exist in Britain. Yet farmers are the countryside's stewards. They take amazingly good care of it.”

Another political gripe is the legislative approach to combating knife crime, something he feels very strongly about.

“I don't think banning things works. When you ban something, you take away the opportunity to have a dialogue about it. Education is the way forward, not legislation. One of the things I do is to teach people to use knives in the outdoors. For us it's not a weapon, it's a tool. It's already illegal to stab someone - the law is perfectly adequate. We're not dealing with the social problem behind the environment. What we need in the world is much brighter leadership.”

And Mears, who grew up in the green belt and is no stranger to dinner at The Ivy, is well qualified to talk about city life, because he has always enjoyed the pleasures of town as well as country - heavens, he's so urban he's even had a spat with a well-known young chef over the injudicious use of wild foods in fashionable London kitchens.

“I love London. I think London is the most beautiful city on Earth. You can do anything in London - there's such knowledge. Libraries, brilliant museums.”

And he is keen to stress that bushcraft skills can be as useful in urban environments as rural ones. “Observation skills, especially, will help you keep safe in a city.” Having taught survival skills to people of all ages for the past 25 years (see woodlore.co.uk), he knows they can build certain qualities that he feels are missing in today's “convenience” society.

“I think that stoicism is something we've lost. It comes from being out. Something always goes wrong, and there's no point moaning, because what does it achieve? There's no one to listen. It's not going to get you anywhere. You've still got to put right what's gone wrong. You have no alternative. So you learn to be stoic like the Indian is.”

Something else he has learnt is that women - who make up 30 per cent of his students (“it should be 50”, he says, emphatically) have a crucial role to play in keeping these skills alive. “Women usually do extremely well at bushcraft. They have strengths that men don't have. There are things that each gender is particularly well suited to, and it shows. In a way, it's a justification of the teamwork between man and woman. That's one of the joys of it.”

As he talks - softly, as he always does in the woods - his knives glisten in a well-oiled belt around his waist, ready to skin or winnow at a moment's notice. And his ever-watchful eyes will often alight on a particular bird or plant, bringing conversation to a rapt halt.

But we're here to talk about Ray Mears Goes Walkabout, the fruit of a lifelong interest in Australia. His handsomest book yet, it is illustrated with his own excellent photography and tells the stories of the unsung heroes, white and black, of Outback survival, who feature in his new four-part BBC2 TV series (from May 25, 8pm). Mears is a passionate - though not blinkered - defender of the continent's indigenous population, whose problems with alcohol, housing and delinquency he sees mirrored in our own cities.

“Some of the people we worked with in Western Australia were, sadly, near to the stereotype of modern Aboriginals. There were a lot of alcohol problems, and when we went tracking with them, I was tracking better than they were.”

So they're losing the skills as fast as you're learning them?

“Yes, but that certainly isn't the story all across Australia.”

And although a stated enemy of hippyish thinking, he is clearly in awe of the Aboriginal belief system. “Their cosmology, their world view, is very complicated compared to others. The more I see of it the more I realise how many levels of awareness that they possess. People often criticise Aboriginals, saying: ‘Oh, they just sit around on street corners chatting...' But they're not just chatting. They're sharing each other's languages. One woman I met could speak 14 of them. But if she were observed by someone with no knowledge of that, they would judge her as they saw her. Learn to judge people by their standards, not ours, and then it becomes interesting.”

As the shadows start to lengthen, Ray suggests we get something to eat, and leads the way to a luscious riverbank where lady's smock grows. We pop the tiny blue flowers into our mouths like sweeties (and I discover the true meaning of the word mustardy) before splitting open a head of wild garlic to reveal the surprisingly sweet little buds within. Then, as we are chomping on sprigs of rich, dark water-mint, a tiny green shoot catches Ray's eye. So he whips out his knife, snaps a branch off a tree, fashions it into a perfectly pointed digging stick, and unearths a tiny white root, in one fluid movement.

“I'd have thought it's too early for this,” he mutters, rubbing the mud off it, as I lean in to share the moment. And suddenly my years of religious Mears-watching pays off. I know what it is.

“It's a pignut!” I cry, triumphant.

“Yes, it is. The first of the year. Here, you eat it.”

And so ended a beautiful day with a remarkable man. A man who, in the skills he has learnt in these last years of there being such a thing as untouched indigenous culture, is a living conduit of the most precious knowledge on Earth. And having been fed the first pignut of the year by him, I am looking for a new goal in life.

Ray Mears Goes Walkabout
Hodder & Stoughton, £20 Buy the book here

Free food: the forager's springtime menu

Lady's smock (Cardamine pratensis). Overwinters throughout the UK with a rosette of dark, round leaves. Add the tiny mauve flowers to salads in small quantities - they're hot - but discard the oily-tasting leaves.

Pignut (Conopodium majus). Part of the carrot family. Also known as the earth nut, it is often found growing among bluebells. The bean-sized root has a mild, chestnutty flavour and can be eaten raw or cooked. Non-Atkins.

Wild garlic (Allium ursinium). Also known as ransomes or ramps. These can be sensed a mile off, but pack a pleasingly sweet punch, even when eaten raw. Wilt the long, luscious leaves like spinach, or eat them raw with the star-like white flowers in salad.

Watermint (Mentha acquatica). Considered sacred by the ancient Druids, this is the grandmother from which most of our hybridised garden mints descend, and is a welcome palate-cleanser after some of nature's spicier offerings. Mears even suggests freezing a single baby mint leaf in an ice cube for your sundowner.

Rose-bay willow-herb (Epilobium angustifolium). An abundant wayside snack whose tall stalks topped with bright pink flowers are recognisable all over Britain. Split the stem open and scrape out the pith with your thumbnail for a sugary, cucumbery pick-me-up on a long walk.

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