Despite Leakey’s excitement over Goodall’s early findings, not everyone was ready to embrace them. In late 1961, she arrived in Cambridge, where Leakey had used his connections to enrol her for a doctorate – not something Goodall wanted to do. “I was only doing this thesis for Leakey’s sake. I’d never had an ambition to be a scientist and be part of academia.”

The patronising treatment Goodall received at the hands of her mainly male colleagues can hardly have endeared her to the academic lifestyle. She was criticised for giving her study-animals names and personalities. “I didn’t give them personalities, I merely described their personalities,” she counters. As for Goodall’s reported discovery that chimps used tools: “Some scientists actually said I must have taught them.” She laughs. “That would have been fabulous if I could have done that.”

I try to imagine receiving this kind of dismissive treatment, and suspect I would have been infuriated, then crushed. Not Goodall. She says she simply knew that she was right and her critics were wrong. I ask where this conviction came from and, as an explanation, she returns to her youth.

“My mother always taught us that if people don’t agree with you, the important thing is to listen to them. But if you’ve listened to them carefully and you still think that you’re right, then you must have the courage of your convictions.”

So when her Cambridge colleagues told her she couldn’t talk about chimps having personality, mind and emotion, she begged to differ – because of Rusty the black mongrel. “Rusty had taught me otherwise. If you spend time with animals, you’re not going to betray them by taking away something which is theirs.”

Rusty, I discover, was one of two dogs with whom Goodall became friendly in her early teens at The Birches. The other, Budleigh, was a beautiful long-haired collie belonging to the owner of the local sweetshop. “Collies are meant to be bright but he wasn’t,” Goodall says, recalling how Budleigh proved incapable of learning to shake hands.

One day, though, as Goodall continued her efforts to train “Buds”, Rusty the mongrel (watching at a distance) raised his paw. “From that moment I realised Rusty was brilliantly intelligent because, even though I wasn’t teaching him, he’d learned by observing my teaching of Buds.”

I am struck by what Goodall did next. The young teenager imagined herself inside Rusty’s mind, she says, in an effort to see the world from his perspective and relive the intellectual feat he’d just performed. There are not many children I know who’d do this, I suggest. She considers for a moment: “Probably not.”

If her Cambridge colleagues had been patronising, it was nothing compared to the treatment she received at a symposium on primates held at the Zoological Society of London in April 1962. “I gave my first scientific presentation and was terrified, says Goodall. “I practised for hours,” she says. “I was determined not to read and not to say ‘er’ or ‘um’. I have remained true to that ever since.”

After three days of talks, the meeting came to a close with a speech by Sir Solly Zuckerman, an anatomist who had studied monkeys in Africa, and gone on to become secretary of the Society and chief science adviser to the Ministry of Defence. Although Goodall had been well received, Zuckerman took the opportunity to fire a volley of pointed comments at the twentysomething newcomer.

“There are those who are here and who prefer anecdote – and what I must confess I regard as sometimes unbounded speculation,” he told his audience, as recounted in Dale Peterson’s biography of Goodall, The Woman Who Redefined Man. “In scientific work it is far safer to base one’s major conclusions and generalisations on a concordant and large body of data than on a few contradictory and isolated observations, the explanation of which sometimes leaves a little to be desired.”

At the mention of Zuckerman, Goodall’s features sharpen slightly, and the pace of her speech quickens. She dismisses his monkey work as “rubbish”. It is the only bad word she has to say about anyone, and even then she controls the emotion almost before it has appeared.

This was not Goodall’s first run-in with Zuckerman. At the end of 1961, there had been a press conference at London Zoo to announce her preliminary findings – and she had hatched a plan to use this public platform to call for an improvement in the conditions of the captive chimps at the zoo. “There was a bare cage with a cement floor,” she explains. During the summer months, the chimps had no shade: “It got boiling hot and there was only one platform, the other had broken, so the male got that and the female had to sit on the floor. It was horrible.”

Before the meeting, over dinner with the diplomat Malcolm MacDonald (who had visited her briefly in Gombe and would become Governor-General of Kenya in 1963), Goodall shared her intention to champion the welfare of the captive chimps: “I was really excited.”

But MacDonald, with his experience as a politician, could see a flaw. Speaking out on behalf of the chimps to a packed auditorium would be a direct criticism of Zuckerman’s leadership of the zoo. “Do you think he’s going to allow a little whipper-snapper who doesn’t even have a degree to tell him he’s in the wrong?” Goodall recalls MacDonald telling her. “You’ll make an enemy for life, and you don’t want an enemy like that.”

Instead, Goodall suggested several simple changes to the chimps’ enclosure that would improve their welfare, and MacDonald worked behind the scenes to see them implemented. “What I learned then is: don’t let people lose face, don’t try to do something publicly until you’ve tried every which way to do it quietly. I’ve found that so helpful to me,” she says, particularly in places like Africa and China.

Naturally, Zuckerman took the credit for the improvements to the chimps’ enclosure. “I don’t mind two hoots as long as it gets done,” Goodall says.

Jane Goodall studies an African baboon, 1974. © Fotos International/Getty Images

A capacity for seeing the bigger picture may go some way to explaining her success as an activist. She pinpoints her transformation to 1986, and a chimpanzee conference organised by the Chicago Academy of Sciences to coincide with the publication of The Chimpanzees of Gombe. By then, she’d spent more than 25 years in the field, completed her PhD, established the Gombe Stream Research Center, got married, raised a son and made further groundbreaking observations on chimpanzee society – including insights into chimp communication, sex, mother–infant bonding, inter-community warfare and cannibalism. But at the age of 52, she walked away from the field and turned to a life on the road. “How ridiculous, really, when you think about it,” she says. “What did I think I could do, trotting around Africa with an exhibit of old pictures blown up, and bits of rock and stick?”

Her initial focus – facilitated by the Jane Goodall Institute she’d established almost a decade earlier to support her chimp research at Gombe – was to draw attention to the plight of chimpanzees more generally. In the wild, habitat destruction, the bushmeat trade and animal trafficking all posed significant threats to the species’ future – and they still do. “It is horrendous.”

Even now, China is asking African governments for chimpanzees and gorillas for entertainment, Goodall tells me. “We feel our sanctuaries, which cost us so much money, aren’t safe any more.”

I find myself being sucked into a vortex of gloom, but Goodall is always ready to offer a reason for hope – a word that crops up time and again in the titles of her many books. One reason is what she calls “the resilience of nature”; by way of illustration, she tells me about land reforms in Tanzania in the 1970s that resulted in widespread deforestation around the Gombe Stream Chimpanzee Reserve.

“When I looked down,” she recalls of one visit, “it was so totally shocking to see our little oasis of Gombe… It looked like a dust bowl: completely bare hills, overfarmed, more people living there than the land could support.”

Today, however, as a result of the Lake Tanganyika Catchment, Reforestation and Education Project, which her Institute began in 1994, the Gombe chimps now have “three to four times more forest than they had ten years ago. It’s regenerated so quickly. So we have 30-foot-high trees.” I feel better already.

More than half a century since she first engineered improvements to the conditions of the chimpanzees at London Zoo, Goodall is still fighting hard on behalf of captive chimps too. In the 1980s, she raised ethical concerns about their use in xenotransplanation, which led the medical community to steer away from this practice. More recently, she has worked with Francis Collins, Director of the National Institutes of Health in the US, to phase out their use of captive chimpanzees in medical research; she is delighted the US Senate voted to increase the budget available for retirement of these chimps. “We are beginning to win,” she says.

I ask Goodall if she is in favour of a blanket ban on the use of chimpanzees in medical research. “I can’t quite say that. But what I can say is that, ethically and morally, I feel it’s wrong to use them, and it’s absolutely wrong to put them in five-foot by five-foot cages.”

Goodall puts chimps at the forefront of the wider debate about the use of experimental animals. “At one time, the scientists said we’ll always need animals for this – and now we don’t,” she says. “If science really puts its mind to getting alternatives… once they do, they’re cheaper and usually safer.”