Known as "garras", or hook sculptures, they were used as hunting and fishing aids for the local nomadic Biami community, and appealed to the then-45-year-old naturalist's artistic bent.

Forty-five years later – Sir David recently turned 90 – these sculptures are now on display in the National Gallery of Australia, after he generously donated them in recognition of the gallery's recent exhibition on the art of the Sepik River.

It turns out the world-famous television personality is a long-time fan of the National Gallery, and takes a keen interest in its Pacific and south-east Asian collection.

Curator Crispin Howarth, who knows Sir David personally, said works of this kind were rarely seen in Australian museum or gallery collections.

"This is an area which wasn't really contacted by patrols until the very first Australian government patrol through this area, the territory of New Guinea at the time was in late 1962, so none of these things found their way into our museums," he said.

Sir David embarked on the expedition to the southern hinterlands of the Sepik River in Papua New Guinea in 1971.

"This was to make contact with communities which live a semi-nomadic life, up in the hills there, and to create the first government contact," Mr Howarth said.

"David Attenborough had travelled during his own television life to PNG, but he'd never had a chance to go to this area before … this was the last of that golden age of really big expeditions."

The journey took six weeks, and took the crew to areas that had rarely or never been visited by white people.

"It was during this expedition, because David has quite a passion for art from the Pacific region, along with all his other very many passions, that he managed to find several objects in a village called Inaro, and he acquired three wonderful sculptures," he said.

"He purchased them off the people who owned them at the time in the village he was staying at. I've got his notes and his diary and so on, he did these beautiful sketches of them, sat and talked and learnt a bit of the context and what they were used for and so on. He takes a really genuine interest in things, he does."

Cut to the present day, when Mr Howarth was visiting England, and Sir David invited him to his house to talk about the gallery's recent exhibition, Myth + Magic: Art of the Sepik River.

"We had a wonderful afternoon, and he pulled out of a side room these three wonderful objects, and he said, 'Look, I was very impressed with what you're doing down there, so would you like these'?" he said.

The works are now on public display, and eagle-eyed visitors will observe that the notes on display state that they were donated simply by David Attenborough, the man himself having insisted on eschewing his official title.

Crispin Howarth will be delivering a lecture about Sepik masks and Sir David Attenborough's 1971 expedition at the National Gallery on June 25 at 2pm. Entry is free but bookings are essential. Visit nga.gov.au for more information.