In between, we’d been talking about Elephant Complex, his brilliant new book about an island that has a geography from heaven and a history from hell. Over the past two millennia, there has scarcely been a century in which Sri Lanka wasn’t occupied, invaded or riven by war. Yet even after the most recent conflict (1983-2009), he says, it’s Paradise Damaged rather than Lost.

“It’s difficult to imagine a landscape that has what it’s got to such a full extent, and it’s only the size of Ireland. It rises to 2,500 metres, it’s rimmed with sandy beaches, it has huge areas of pristine bush and forest. It has 5,800 wild elephants wandering around, the biggest concentration of leopards in the world. It’s the most amazing garden of a place.”

That garden, beguiling to the casual visitor, is one where anyone who digs as diligently as Gimlette does will make troubling finds. Like earlier books, which took him to places as various as Paraguay and Newfoundland, this one has a great cast of characters, from tribesmen to terrorists.

It displays his gift for graphic imagery (“a tree full of flying foxes, huge dollops of black draped in the branches like a Jesuit laundry”) and his eye for the absurd (a deal under which the Sri Lankan government and the Tamil Tigers worked together to rid themselves of Indian peacekeepers – so that they could get on with fighting each other). But it is, perhaps, his darkest book yet, dealing not just with the civil war and its aftermath and the tsunami of December 2004 but with child prostitutes, of which charities estimate the country has at least 15,000.

“Sri Lanka,” he says, “is probably the most beautiful country I’ve ever been to. It has the best food, some of the most charming people that I’ve ever known. There’s a wonderful serenity, as far as the visitor is concerned, but there’s a sort of rage below the surface. There was a story in the newspaper while I was there of a man who put up with his neighbour dumping rubbish over the fence for 20 years, and then just cracked and went round and killed her. I wouldn’t say that’s typical of Sri Lanka, but it says something about [the country] that it could happen there.”

He had, he says, a strong sense of attempting to penetrate a community that seemed in one sense “medieval”. “I was very wary at first that there was a lot I didn’t understand, and perhaps would never understand. I don’t think I ever really got over that, but I did learn to live with it.”

He did feel, however, that by the end of his three-month stay he knew the landscape better than many natives did. Starting in Colombo, he went on to Kandy and the hill country (including the British-built town of Nuwara Eliya, “where the elite go to be cold and damp and imagine they’re in England”), the south west and the tsunami-ravaged south-east coast, and Jaffna and the north.

“A lot of people in Colombo,” he says, “have never really travelled outside other than to visit the village their family comes from. People aren’t naturally inclined to travel the island – except the wealthy. The war has also taken its toll. For much of the past 30 years even the wealthy never really explored much. When they talk about going to the beach, they’re talking about Wellawatte, which is about 10 miles outside Colombo.

“They simply don’t know what goes on elsewhere. So although places like Trincomalee have fantastic beaches, most of the people I met in Colombo have no idea about them and have never been there. They’re just beginning to explore that side of their own country. They all tell you that it’s the most beautiful, wonderful place in the world – and they’re right. But they don’t actually know that.”

He’s pleased that in the latest election the Tamils and Muslims were able to join coalitions and give themselves some political strength in a country where, for too long, democracy has meant no more than keeping the majority happy. He’s keen to encourage British travellers to visit, and to do what they can to help the economy.

Not for nothing, he says, is Sri Lanka known as “India Lite”: “It’s much easier to travel there. Transactions go much more smoothly, things work, trains and planes do leave pretty well on time. And there’s a fantastic network of hotels, all available on the web.”

He points out, though, that enterprises run by the navy and the army include hotels, diving schools and even the hire of plastic swan-shaped pedalos on Beira Lake in Colombo. “I’d encourage people to avoid them – not because the army and navy are bad; I met very good people in both – but because it’s unfair competition. They use state resources and so make life difficult for anyone else in the trade.”

But not for the tourist. “In a superficial way,” he says, “you could enjoy an amazing trip there without being aware of any of the dark side of Sri Lanka at all.”

You could, but I wouldn’t advise it. Along with the swimming trunks and the sunblock, I’d pack a copy of Elephant Complex.

(Michael Kerr - Telegraph)