For what might well be the most famous farm on earth, Diddly Squat – or Curdle Hill Farm, to give it its old name – is remarkably approachable. The mainline station is only 10 minutes away. It is listed on Google maps, albeit with a parenthesis that says it is not open to the public, but a public right of way passes through it. Any rambler might catch a view of the cast of Clarkson’s Farm, the enormous Lamborghini tractors, or the sign, posted high on a shed wall: anyone found dropping litter will be shot in the face! Or even of the farmhouse, the honey-stone pile where the farmer, Jeremy Clarkson, lives.

To the millions who followed Clarkson’s Farm over the three series that have aired on Amazon, this is tantamount to holy ground. That’s where Kaleb, Clarkson’s lovable boy-wonder farm manager, parks his car. Those are the bags full of nitro. That’s a cow.

This ease of access has created problems, Clarkson explains, when we sit down after he has acceded to a few photographs.

“When the house had just been finished, Lisa [Clarkson’s partner] was in her bathroom and this couple just walked in,” he recalls. “They said, ‘We thought we’d have a look around.’ I know it’s nice to look around somebody’s house, but not when you haven’t knocked on the door. It’s weird, is what it is. They were perfectly pleasant, and they simply couldn’t see that they were doing anything wrong.”

If they felt a curious sense of entitlement, it is because at 65 Clarkson is one of those figures who is so familiar he seems to have passed into national ownership, like a kind of truculent utility. The no-nonsense, middle-aged British bloke uniform is reassuringly familiar: loose checked shirt, desert boots, long Easter Island-statue of a head beneath thinning grey curls. Tall as ever, he is less imposing in person than on television. Mellower, too. Then there’s the cadence of his sentences, an inflection – as with Ricky Gervais’s David Brent – that has seeped into everyday speech.

You might not think Jeremy Clarkson could still amuse you with a simple reversal at the end of a long paragraph. You might say: he’s been on telly for 40 years, he has written two columns a week for nearly as long, he has written countless bestsellers. He has no gas in the tank. But you’d be wrong.

This ought to be a promising moment to talk to him. The fourth series of Clarkson’s Farm has just come out on Amazon. It is full of unexpected new problems, not least Kaleb’s new-found stardom (he is absent from the first two episodes as he’s on tour) and the difficulties of opening a pub, which Clarkson has said makes farming look easy.