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By Giles Badger, Producer on Seven Worlds, One Planet

Revealing the secret lives of ‘baby dragons’ or olms was a major goal for the Europe team, but filming these mythical creatures came with fundamental challenges.

These blind salamanders, some 20 centimetres long, are only found living underground, and underwater, in the depths of Slovenia's caves. And despite having no eyes, they are extremely sensitive to both light and electrical impulses emitted by camera technology.

Little is known about these animals in the wild, but scientists at Postojna cave had an idea where they would likely be. The crew scouted the caves to check both for the presence of olms and the water clarity. A quick flash of a torch revealed that the water was particularly clear in one of the caves and also just how sensitive the olms were to light!

With a filming location identified, the Seven Worlds crew dragged an inflatable dingy and twenty bags of filming and dive gear through miles of slippery tunnels... Some of the squeezes were so small that kit had to be repacked just to fit through.

To avoid disturbing the animals the crew needed to keep lighting to an absolute minimum. Armed with one of the most sensitive cameras in the industry- Cameraman Gavin Newman devised an onboard lighting rig that was no brighter than a candle.

Water temperature was a chilly 8 degrees Celsius, but happily for Gavin and the director, the underground lake was full of olms. Gavin counted over fifty in a single dive but getting the close up shots the director wanted wasn’t possible.

Postojna’s underground research centre offered the perfect solution.

Scientists here are studying both the breeding ecology and limb re-generation of these remarkable animals to help conserve them, and its large tanks are fed with cave water, so crucially the olms are accustomed to low levels of light and they are habituated to people.

Cameraman Jonathan Jones was able to be within centimetres of olms, and use lighting necessary for close up macro photography, and do so without disturbing the animals. This way the Seven Worlds team were able to show the olm in a way that had never been done before and complete a magical sequence!