In the hot summer of 1976, when Richard Sabin was 10, he went on a trip with his Birmingham primary school to the Natural History Museum in London. Blown away by the scale of what he was seeing, the wide-eyed schoolboy was told by an attendant that if he wanted to see something really big he should make his way to the mammal hall, where the skeletons of a number of whales, including an enormous blue whale, were displayed.

“Another gallery attendant went past, and I stopped her and said, ‘Are these real?’” recalls Sabin. “And she said, ‘Yes they are. They’re the real skeletons of animals that still live in our oceans today.’ That was the sentence that really grabbed me and carried me away. I didn’t know what to make of what I was seeing. I was transfixed.”

Facebook Twitter Pinterest The blue whale in her final position in Hintze Hall. Photograph: BBC/Natural History Museum

More than four decades later, Sabin is the museum’s principal curator of mammals. And on Thursday he will – in a development that would have been “absolutely staggering” to his 10-year-old self – oversee the final touches as the same blue whale skeleton is dramatically suspended from the ceiling as the principal exhibit in the museum’s grand entrance hall, the centrepiece of a major redisplay that the Victorian institution hopes will position it as a gallery of the future.

The decision to hang the 25-metre skeleton, belonging to a female that was beached off the coast of Ireland in 1891, in the grand Hintze Hall has not been without controversy, as it has required the removal of Dippy, the much-loved diplodocus skeleton cast that has commanded the space since 1979, and has become a symbol of the museum to generations of visitors.

But as Sir Michael Dixon, the director of the museum, points out, Dippy is not, in fact a real dinosaur, but a huge 21.3m resin cast of a diplodocus skeleton that was found in Wyoming in 1898 and acquired by the Scottish-American philanthropist Andrew Carnegie for his museum in Pittsburgh. Beloved or not, it’s a fake.

Changing the display, says Dixon, offers “a once-in-a-generation opportunity to slightly reposition the museum”, from being seen as an institution that looks after dusty old bones to one that stresses the urgent need to conserve the natural world. “We’re using this as a springboard ... to restate a modern purpose for the museum, to inspire a love of the natural world and to unlock answers to the biggest issues facing humanity and the planet.”

Facebook Twitter Pinterest Workers attach the blue whale’s mandible bones. Photograph: BBC

As an enormous creature that lived on land and then, about 45m years ago, moved into the ocean, the blue whale as a species is perfectly placed to tell the stories of evolution and the origins and diversity of life on the planet, says Dixon.

But it also makes a critical point about the importance of conservation, he says. “When our whale was alive there were probably 250,000 whales alive in the world’s oceans, and over the next century, until the 1960s, we hunted them practically to the brink of extinction, [until] there were probably only a few hundred left.

“Then, in 1966, at the London meeting of the International Whaling Commission, we took this incredible global decision to stop hunting blue whales, and now the population has recovered to about 20,000, so there are the beginnings of a viable population again. I think that’s a tremendous story about man’s ability to influence our sustainable future, and a model for the kind of thinking that we believe is going to be necessary.

“The kind of decisions we take about our own future over the next decade are probably going to be more important than any decisions we have taken over the next 10,000 years.”

As head of conservation, Lorraine Cornish is responsible for the care of the museum’s 80m specimens, and as such was tasked with ensuring that neither Dippy’s 21.3m cast, nor the even bigger, 4.5-tonne skeleton of the whale, sustained any damage in the move. Dippy is currently in Canada, being fitted with a new metal armature that make it robust enough to tour eight locations across the UK from February next year.

The full story of the installation, which necessitated the closing of the Hintze Hall for more than six months, is told in a Horizon documentary, narrated by Sir David Attenborough, to be screened on Thursday 13 July on BBC2.

At times her task involved delicately dusting the bones with brushes, says Cornish, at times attacking the glue used to stick the resin vertebrae together with hacksaws.

The most tense moment was when the whale skull – an enormous bone made of 46 fused parts, was removed from its location suspended high in the mammals hall and threaded between the cables of other suspended specimens to a secure spot at ground level. “That was a very long day.”

Facebook Twitter Pinterest The flippers are made ready for fitting. Photograph: BBC/Natural History Museum

As the film captures, there was also some anxiety when it was unclear whether the skull, having been fitted with a new (largely invisible) steel frame designed by the same team that made the dinosaurs for the movie Jurassic Park, would fit back through the museum’s surprisingly narrow front door.

At Sabin’s suggestion, the whale has been hung in a dramatic diving pose so that “it looks like it’s coming to meet you”, he says. It will be formally unveiled to VIPs including Attenborough and the museum’s patron, the Duchess of Cambridge, at a reception on Thursday night.

For Sabin, however, the important moment will be when the doors of Hintze Hall are reopened for the first time to members of the public on Friday morning. “I guarantee I am going to be standing somewhere near those front doors to hear what people have got to say when they walk in. But what I am really looking forward to is the reaction of the kids.

“When we did the final bit of the installation and it was hoisted to its final position, we stepped back and looked up, and I was really overcome. I felt like that 10-year-old boy again. That’s our objective. Inspire other 10-year-old boys and girls, get them into marine science, get them working for the future.”