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On May 20, 1989, writer Henning Mankell opened a telephone directory and began looking for a name. Any name. Mankell had decided to turn his hand to crime fiction. He needed a policeman, and the policeman needed a name.

He rifled through the book and stopped at W. Then he moved his fingers across one page until he came to the name Wallander. And there he stopped.

Thus life was first breathed into Kurt Wallander, Sweden's fabulously grumpy, dysfunctional fictional detective.

More than 25 million copies of Wallander novels have been sold since Mankell created the character and featured him in Faceless Killers, published in 1991. In the process the author has become Sweden's most successful literary export.

In the southern town of Ystad, where the books are set, there are guided tours of "Wallander country", much to Mankell's embarrassment, while the books have been televised at home, with Krister Henriksson as the tortured detective.

Now Wallander has been given a further lease of life in the guise of Kenneth Branagh, who plays the detective in the BBC series, a television outing that has garnered strong praise. Nor is it hard to see why. Branagh is as powerful a screen presence as one could wish, while other performances - especially David Warner as Wallander's fragile, vulnerable father - are first-rate.

Not everything is perfect, of course: the dialogue is woeful, while scenes from each episode seem to have been filmed at random times of the year.

One minute frost is covering the ground, the next fields are filled with wheat. For all these deficiencies, however, Wallander is a hit.

But why? What are the complexities of this dark, humourless misanthrope that make him so endearing to British audiences? Why should the bleak Swedish psyche be so appealing to viewers? Even Mankell admits that he dislikes the messily divorced, diabetic fast-food addict that he created from his perusals of telephone directories.

"I would rather be friends with Sherlock Holmes," the author once remarked.

So what is the attraction? According to publisher and writer Julian Evans, an expert on European fiction, it is Wallander's uncompromising self-destruction that so fascinates.

"He's quite unsalvageable, Wallander, in a way very, very few fictional characters really are. In an existential sense, he seems close to the end, all the time. You can't say that at all of all detectives. His woeful relationship with his daughter ... his inability to manage any female relationship. Every crime he solves or fails to solve, you still think the next thing he is going to do is just ... die."

This is a man permanently on the edge, "a sort of walking open wound", as Branagh describes his character, and he makes absorbing television.

Then there is the background: the bleak, unforgiving soil of Sweden's Skane region in the south.

"Border areas have a dynamism all their own," Mankell says. "They set off a reflex of unease."

And Mankell certainly knows a thing or two about borders. Born in 1948 and raised from the age of two by his father Ivan, a judge, after Henning's mother had walked out on the family, the author-to-be joined the Merchant Navy at 16 in 1964 and became a stevedore on a coal and iron ore freighter.

This was his "real university", he claims. A couple of years later, he arrived in Paris and stayed for the riots and student activism that were to grip the city in 1968. It was to be a formative period. As his publisher, Dan Israel, has remarked: "Henning and I are children of 1968."

The author returned to Sweden to become a playwright and author, publishing his first novel, The Stone-Blaster, at 24. He later travelled extensively in Africa and in 1987 was asked to run the Teatro Avenida in Maputo, Mozambique. He has held that post ever since, dividing his time between Africa and his farm near Ystad, in Sweden, writing his books in both locations.

Thus, half of the Wallander novels - with their vivid evocations of the bleak Swedish landscape and their chilling stories of serial murder - have been written in Africa, a striking contrast, to say the least, although for his part Mankell finds nothing unusual in this geographical dichotomy.

"When I [first] got off the airplane in Africa, I had a curious feeling of coming home," he once said.

Over the years, the author has had a string of affairs and has fathered four children by four different mothers, although he insists, emphatically, that his current marriage - to Ingmar Bergman's daughter Eva - will be "the last".

Bergman turns out to have been a fan of the Wallander books - as is just about every Swede, it seems. Mankell recalls walking down a street in Stockholm during a referendum about joining the EU and being approached politely by a man in his 60s, who asked whether Mr Wallander would vote yes or no.

"That was the moment I grasped the size of the character," says the author.

His appeal is harder to assess, however. It is not simple travelogue, Evans insists.

"I reject the argument that Wallander is popular here because there's a kind of 'northern' fiction, particularly crime fiction," says Evans.

It is the mental landscape that he inhabits that gives him such appeal, he argues.

In addition, there is the simple issue of availability in key book buying markets.

"I think it's cyclical," says Evans.

"We've taken a long time away from European art, European fiction in particular. We had our eyes to the Americas. Part of the problem is simply the translation. There has been truly great stuff going on in European fiction for 15 years or more, and perhaps it's only now we're beginning to let it in."

There is more to the issue than that, however. Many other novels about foreign detectives are now translated into English and none has had the impact of those involving the resolutely depressive Kurt Wallander.

In that sense, Mankell has bigger issues to address than the average detective novelist, which perhaps explains his elusive appeal. Mankell is, to repeat the description of his publisher, a child of 1968.

"The fundamental driving force for me is to create a change in the world we live in ... it is about exploitation, plundering and degradation," he says.

"I have a small possibility to participate in the resistance. Most of the things that I do are part of a resistance, a form of solidarity work."

His books, and the series made from them, are investigations of the failure of political promise, say critics.

"All of Henning's books are an elegy to the broken socialist dream of Sweden," the publisher Christopher MacLehose remarked recently. "Henning still can't get used to the idea that Sweden has failed to deliver its social democratic dream."

Thus we get more than a mere who-dunnit with a Wallander story. We get edge, a sense that a good man is hunting through a landscape of broken dreams for signs that some decency has survived and who rarely succeeds in his quest.

There is a resonance here that goes far beyond standard detective novels.