Bertie Gregory could scarcely believe his eyes. While making his captivating new series, Secrets of the Penguins, the British Emmy and BAFTA award-winning cinematographer witnessed an absolutely astonishing example of animal behaviour. In the process, he became the first person ever to capture it on film.

Bertie was tracking a colony of hundreds of young emperor penguins in the most hostile conditions this planet has to offer. The director was braving phenomenally challenging temperatures of -54°C. It was so freezing, sheets of ice had formed on the penguins’ coats.

The director had been filming the chicks for many weeks as they trekked across the bitterly inhospitable Ekström Ice Shelf in Antarctica, the coldest place on earth. They were heading towards the Southern Ocean to take their first swim and turn into adult penguins.

What happened next, though, was utterly breathtaking. The director, 31, says that it was definitely, “Not in the script. Penguins famously don't read the script. It’s very annoying, actually! They go, ‘I'm not going to do that, but I'm going to do something even more crazy instead!’”

Talking exclusively to the Daily Express, Bertie continues: “Normally young penguins take their first swim by jumping off the sea ice, which is a one or two-foot-high drop, and that was what we planned to film. [But] one group of several 100 chicks had taken a wrong turn on their way to the ocean and found themselves at the top of this enormous, 50-foot-high ice cliff.”

Unsurprisingly, the stranded young penguins froze at the cliff’s edge. This unforeseen situation was obviously terrifying, but they took the plunge into the unknown anyway. 

“What's crazy is these penguins haven’t swum before,” Bertie says. “This is the first time they've even seen the sea, and there are no adults showing them the way. That's why they took the wrong turn.

“It's like taking your kids for their first swimming lesson, and you're told that the instructor has not turned up today, and they’re not starting in the shallow end – they have got to jump off the Olympic diving board. But that's exactly what these chicks did. Absolutely bonkers!”

What drove the birds to take such a death-defying leap of faith, then? “Penguins forge these bonds of friendships, so as soon as one jumped, the rest of them must have thought, ‘Oh yeah, Barry survived. We can do it too.’”

Bertie, who has previously shot beautiful wildlife films Billy & Molly: An Otter Love Story, Planet Earth III, Frozen Planet II and Seven Worlds, One Planet, was mightily impressed by the chicks’ sheer fearlessness. 

“Some of them jumped off very gracefully – a 10 out of 10 judge score from the Olympic diving judges. But some of them got zero points for style. They just fell over backwards,” he says.

“What was going through my brain at the time? This had never been filmed before, so I didn't know if the chicks could survive a fall from that height. We'd watched these chicks grow up, and I was definitely emotionally attached to them. And so, it was initially not a very enjoyable experience.”

But as he watched through a lens, his heart in his mouth, something unbelievable happened.

“I realized they had landed safely in the water. To me, the coolest part was not when they jumped; the coolest part was a few moments later when they popped back up to the surface having made an enormous splash.

“Penguins instinctively know how to swim. So all of a sudden, when they hit the water, this switch just went off. They went from being a flappy mess to, ‘Oh, hang on, I am designed to be one of the world's greatest free divers.’”

Almost immediately afterwards, they were holding their breath and diving down. “Emperor penguins dive deeper than any other bird. They can go down to 500 metres, and hold their breath for 20 minutes,” adds Bertie. “It was an amazing moment to witness. I thought, ‘Wow, what a secret we've managed to capture!’”

This stunning moment is not the only world first filmed by Bertie and his team. His series uncovers many secret penguin behaviours that have never been caught on camera before.

We may think we know all about these widely loved birds – there have, after all, been many series about them before. But Secrets of the Penguins, whose executive producer is Academy Award-winning director James Cameron, reveals there is far more to these adorable creatures than we ever imagined.

Another extraordinary behaviour filmed for the first time ever in the documentary is a moment of great tenderness between a couple of bonded adult emperor penguins. Having courted by mimicking each other’s movements in the most touching manner, the pair prepare to look after the single egg they will produce each year.

Remarkably, in emperor penguin society, it is the fathers who incubate the egg until it hatches. If the egg spends more than 60 seconds on the ice, the chick inside will die. So its father must take the egg from its mother and keep it off the ice in a featherless patch between its legs called a brood pouch.

Bertie’s team shot a couple practising the handover of the egg from mother to father with a snowball. It is a never-before-seen sequence guaranteed to make the hairs on the back of your neck stand on end.

The selflessness of the father after he receives the (real) egg is remarkable. As he is battered by the 120 mile an hour winds, he forgoes food as he sits on the egg for two months while the mother regains her strength by hunting at sea.

At the same time, in an act of astounding cooperation, 5,000 fathers huddle together to insulate themselves and protect their eggs. Bertie calls it “one of nature’s great spectacles.”The director shot another outstanding sequence for Secrets of the Penguins in the Galapagos Islands.

“Galapagos penguins have basically learned that, rather than hunting for themselves, they can get a much easier meal if they just follow big brown pelicans around.

“The pelicans will dive into the water and grab a huge mouthful of fish. But while they sieve the fish out of the water, they are stuck and can't fly away,” he says. “These tiny little birds come zooming over to this massive pelican and start stealing the fish out of the side of its beak. I loved watching these sassy little creatures mugging a pelican!”

Drawing on the expertise of 70 scientists and wildlife filmmakers, Secrets of the Penguins was a gargantuan undertaking. It was shot over a period of two years, in such diverse places as Cape Town, Namibia, and South Georgia, as well as Antarctica and the Galapagos.

The three-part series, which is available on Disney+ and will air on Nat Geographic Wild on Sunday at 9pm, was often exceedingly hard to make. Bertie spent 274 gruelling days shooting in the Antarctic.

One surprising moment stood out the toughest. “I went 51 days without a shower because with the tent I had the only way of having a shower was a bucket outside, and I just couldn't face being any more cold than I already was,” he laughs. “Fortunately, there's less bacteria in Antarctica than there is in the UK, so I didn't smell bad until I got home!”

Secrets of the Penguins taps into our passion for these innately charismatic birds. “They look like they have little tuxedos on, and they're hilarious to be around. They’re comical and clumsy, and they're always tripping over and falling on their faces,” smiles Bertie.

He believes we warm to these creatures in the coldest location on the planet because of their very human capacity for friendship.

“They have these incredible bonds, not just between males and females, but between males. But the bond I love most is between the chicks,” he says. “When the chicks are five months old, they're abandoned by their parents, and you think they would be alone, but they're not. They've got each other, and they form these awesome little friendships. 

“Just like human friends, they gain confidence from each other, and they overcome obstacles together. As soon as one of them figures out how to do something, the rest of them copy it. It's wonderful to watch.”

In the series, a tiny abandoned chick is shielded from the icy wind by a phalanx of his pals. The filmmaker says: “His parents might have gone, but his friends are standing by him. You can't help but get attached to these birds. They're so cute and you really get to know them as individuals.”

Secrets of the Penguins shows us many new and very surprising aspects of their lives. “The takeaway is that I hope people enjoy the magic of the penguin,” Bertie observes. “I thought I knew penguins coming into this project. But I was so wrong.

That is clearly why he is able to put up with filming for so long in such exceptionally harsh conditions.

“Exactly,” Bertie laughs. “Showers – who needs them?”

 All three episodes of Secrets of the Penguins are available now on Disney+ and will air on Nat Geo Wild on Sunday at 9pm.