As David Attenborough launches his new series, Anna Fazackerley finds out why he is the academy's favourite broadcaster

His hushed, mellifluous voice has become synonymous with natural history. He hugged a gorilla and people everywhere fell in love with the animal for the first time. He explored the private life of plants and there was a flood of interest in studying botany. But Sir David Attenborough, probably the only television populariser to be universally admired by even the snootiest of academics, found his niche entirely by accident.

"I thought I'd be a producer, but I never dreamt of being a specialist. I did politics, religion, knitting - everything," he explains.

"Then in 1954 I was working as a producer, and the presenter of something called Zoo Quest was very ill, so I stood in." He is characteristically blunt about his motivation in doing so. "It struck me as a very nice way to go to Africa."

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Since this unplanned beginning his very public exploration of the natural world has taken Attenborough all over the globe. But he isn't remotely interested in ticking off countries in his atlas. Something more fundamental drives him.

"I've no idea how many countries I've been to," he says rather crossly, sitting in his comfortably old-fashioned living room, where the African objets d'art seem as incongruous as the ultra-sleek widescreen television.

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"The important thing is to have been in a tropical rainforest in Africa. Where it is on the map is neither here nor there."

Those who caricature Attenborough as soft and avuncular misjudge him. Leaning back in his armchair he answers questions abruptly and with sometimes withering authority. It may not have been his vocation, but it is easy to see how he survived as controller of BBC Two in the 1960s and later as director of programmes for both BBC channels.

Attenborough is 79, though he looks ten years younger, and seems frustrated by the fact that his hearing is not as sharp as it used to be. After three years working on his latest BBC series, Life in the Undergrowth , (which he is adamant is about "terrestrial invertebrates" and not insects) he has no intention of retiring to his pretty garden with the pruning shears - or settling down with the remote control.

"I've already started work on the next series, about amphibians and reptiles," he says. "Why would I stop? It's a marvellous way of spending your time. If you can earn a living as well, even better. It is an unbelievable privilege to spend your life doing this sort of thing."

Perhaps this is key to his appeal within the academy. It is not just that Attenborough, unlike many other presenters of so-called educational programmes, can be trusted to get things right. More significantly, he is fuelled by the same unflagging enthusiasm for his subject that animates most researchers.

He has clearly never seen his as a nine-to-five job distinct from home life. While his children were growing up, he spent three months every year away filming, though he maintains that his family was always a priority. He admits he is a workaholic. "I certainly look at what I'm doing and there are few things I enjoy as much. I think I have some degree of the puritan work ethic," he reflects.

It speaks volumes of the respect in which he is held that Attenborough was elected a fellow of the Royal Society - an honour bestowed on few academics, let alone broadcasters. And in a speech last year, Lord May of Oxford, the society's president who is known more for his swearing than for his sycophancy, described Attenborough as a true scientist.

"I can think of no greater compliment," Attenborough says. "I would like very much to feel that I have a proper respect for science and facts. I think science is incredibly exciting."

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He is quick to point out that strictly speaking he can never be regarded as a scientist, because he does not advance scientific knowledge. When he starts creating a television series he has a "general notion" of what he wants to include, and a young graduate researcher finds all the latest scientific work with which to flesh out the skeleton.

But on a personal level he has made "thousands" of discoveries during his career. On awarding him the prestigious Michael Faraday Prize for science communication in 2003, the Royal Society praised his ability to convey "the sense of wonder that drives scientific research". Attenborough sums up the sort of natural history he does as simply "trying to make sense of what is going on around us".

One imagines that having covered most of the big wildlife subjects, the idea of making sense of the tiny creatures that swarm and crawl in the undergrowth must have gone down well in that first programme planning meeting - just think of all those viewers watching through their fingers with horrified, squirming interest. But Attenborough is appalled at the very idea that this might be the attraction. He looks at Life in the Undergrowth , like all his other programmes, with a scientific eye. "We are talking about the evolution of life on the planet," he says passionately.

"They emerged long before my ancestors and established the first ecosystems. They remain the foundation of life on land."

And, like the entomologists and other biologists whose work fed into the series, he is captivated by the individual stories of these creatures.

"Take 17-year cicadas," he says, his speech becoming noticeably faster.

"The larvae live for 17 years underground. Then the entire adult population emerges over the course of a week. We don't know how this synchronicity is achieved. How do they know 17 years have passed? They mate and fall to the ground, and are not seen again for another 17 years."

Until quite recently it would have been impossible to bring the mysterious lives of these tiny invertebrates to our screens in any real detail. But a new generation of highly sensitive electronic cameras and optical systems removes the risk of fierce lighting frying insects alive or stopping them from behaving in a normal fashion. Tiny lenses no bigger than a pin can now move alongside an ant, looking over at the subject as though travelling in the next lane on a motorway. It patently excites Attenborough to be working at the cutting edge.

But his love affair with discovery does not blind him to the harsher realities of working in science in the UK today. He is idealistic about what universities used to be like - and strikingly pessimistic about what they are becoming.

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"I suppose I see universities more as a place for intellectual life than as training schools. Undoubtedly, we are getting away from that," he says.

"The question is, can the pursuit of knowledge survive? My worry is that (the Government's economic mission) could drive out the disinterested research and thought that was so distinctive about academic life."

He says simply: "Energy and drive is the academic quest."

This leads to a chilling notion - that in some ways television broadcasters such as Attenborough have more freedom to pursue the academic quest than academics themselves. When asked if he sees his puritan work ethic as typical of scientists, he says: "Do academics have that? I'm not sure there's any room for such passion now. There used to be in the traditional universities. But is there now?"

Nonetheless, the prospect of collaborating with Attenborough seems to lift the gloom for many scientists. After years in the shadows of bigger and trendier biological areas, entomologists are beside themselves with excitement anticipating what they call "the Attenborough effect". Ever since they first heard about the series, they have been crossing their fingers that the programmes will bring with them increased undergraduate student numbers and remind funders why theirs is a field that is worth nurturing.

Attenborough recognises that he has the ability to influence the research community in this way. "I'm well aware that there was an increase in the number of botanists after my series on plants. And there was an increase in the number of palaeontologists after that series," he says. "That's a great compliment. But if people about to go to university didn't react, I would know I was doing something wrong."

He thinks a lot about his impact on audiences. He sat on the funding committee of Copus, the now-defunct government body that awarded grants for increasing the public understanding of science. And he remains passionate about its mission. "It was a very important proposition. Trying to make science available to the general public is extremely important," he says.

"People who do it well are invaluable."

Putting a value on the programmes Attenborough has presented during his 50-year broadcasting career would be hard. It is estimated that a staggering 500 million people watched his groundbreaking 1979 series Life on Earth . And he has presented a further 14 major series since then.

But he is far from pious about television's educative role. His fascination with the wonders of the natural world may be scientific, yet when it comes to discussing what makes good programming, his persona is very much that of the media professional.

He is unimpressed by the concept of a public service programme, insisting instead that the public can be served only by a varied schedule. If public service means boring, worthy programming, then Attenborough isn't interested.

"I don't think television need educate. And I don't believe in the distinction between education and entertainment," he says.

When asked to suggest an example of a good programme that really taught people something, he picks the long-running prison comedy Porridge . "That was education. It told you a great deal about human nature and prison reform and human abilities and disabilities - but it was also enormously entertaining," he explains.

And he is the first to admit that television can meet different needs at different times. Nodding towards his impressively cinematic television, he says: "One of the purposes of what comes out of that machine is mental soporific - chewing gum for the mind. After a stressful day at the office the last thing I want to have on is a debate about Plato or, for that matter, parasitic wasps."

In fact, he is too busy to watch much television. And when he does he is not one of the millions riveted to reality shows such as Big Brother or makeover programmes such as What Not To Wear .

Becoming more serious again he says: "It would be a great pity if the most powerful method of personal communication the world has ever seen was just used for hype or mindless fodder."

There is a clearly a demand for more thoughtful programming. But what will happen when the most powerful natural history communicator we have ever known finally exits the small screen? The film-maker and politician Lord Puttnam summed it up during a select committee session about the communication of science in 1999. "I have been involved in any number of conversations regarding the whole world of wildlife, where, if you do not have David Attenborough, you do not really have a series," he explained.

Attenborough is too modest to agree, saying that he rates Charlotte Uhlenbroek, the glamorous young presenter of the BBC's Talking with Animals series. He adds that, unlike him, Uhlenbroek has the benefit of an academic background. Nonetheless, the "what next?" question is one that should worry BBC bigwigs and scientists alike.

Looking back on his career Attenborough reflects poignantly: "There are some species of birds of paradise that I would dearly like to film. I never will now. I've been extraordinarily lucky in seeing something like 28 species, but there are 42. They symbolise for me the wonder and astonishment and strangeness of the natural world."

Listening to him in his quiet detached house thousands of miles from the tropical rainforests where he made his name, there seems little doubt.

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Attenborough is simply irreplaceable.

Life in the Undergrowth starts on November 23 at 9pm on BBC1.