First it was flying bird-eating fish.

Now in episode two of Blue Planet II, viewers will see terrifying footage of giant cannibalistic squid feasting on each other in the murky depths of the Pacific ocean.

It is the first time that any film crew has ventured 2,500 feet underwater off the Chilean coast to capture huge shoals of predatory humboldt squid.

The 7ft monsters, who flock to the area to hunt lantern fish, were filmed speeding along in packs at 15mph, attacking cameras and resorting to cannibalism when their food supply runs out. In one scene two humboldt's are seen fighting over a smaller squid.

David Attenborough, who narrates the series said: “When there are no more fish to be found they hunt each other.”

Orla Doherty, producer of ‘The Deep’ episode, said: “We wanted to go way down to meet the Humboldt squid.  We did a stake out off the coast of Chile to find squid which just involved sitting in the darkness.

“These are two metre monsters yes, but they’re these unbelievable beautiful animals. We sat in darkness and we played games with them.

“We had to put a red light on to get them interested and then we had to put the red light off because they got bored and then we had to put the white light on to keep them around us and then we had to put the white light off.

“It was this game with them and eventually we got to see them and film them hunt in their world in these marauding packs which nobody has ever done before. I don’t know if anyone will ever get to do that again.”

The humboldt, which can live in shoals of up to 1,200, is one of the world’s most aggressive predators, equipped with a formidable armoury of eight arms and two long feeding tentacles each covered in hundreds of tooth-lined suckers.

However because they hunt at night in the darkness it has been difficult to capture them in the wild.

BBC producers worked alongside marine scientists to find the location shoals of lantern fish, then sat and waited for hours for the squids to appear.

Blue Planet executive producer James Honeyborne said: “We see what they get up to down there and we couldn’t have done that without the scientists wanting to come along with us and all doing it together.

“So I think there’s a new level of collaboration and that’s why we’re also beginning to film things now that have a value to science because they haven’t been seen before and that makes the whole thing more exciting for us.”

The episode also includes amazing new footage from the deepest dive into the Antarctic ever made, 3280ft below the surface. The crew persisted even when their submarine started leaking and filling up with below-freezing seawater 1,500 feet from the surface.

However their perseverance paid off, and they captured strange fish with anti-freeze in their blood, fields of giant sponges and swarms of krill that glow in the dark.

The strange tale of the Venus flower basket sponge is also told for the first time. Tiny shrimp enter the sponge as larvae but then grow too big to escape and are forced to spend their entire lives trapped inside.

Episode two ‘The Deep’ of Blue Planet II is broadcast on BBC One on Sunday at 8pm.