A four year project to locate and film a German submarine and the Navy vessel it sunk has resulted in a documentary that will premiere in Guernsey in April.

Photographer, film maker and diver Karl Taylor is behind the mission to locate UC-18.

It was a sea mine laying German submarine that was involved in a battle with the Royal Navy's covert vessel the Lady Olive.

That engagement took place in February 2017. Both traded blows and both sunk, without trace, until now.

Karl had to carry out a vast amount of archive research to try to pinpoint the wreck site. Previous attempts had been inconclusive.

Diving to those depths, up to 70 plus metres, means light levels are low, it is technically difficult and has to be done in calm seas and slack tides.

Karl says finding the sub was a dream come true:

"And then we approached the sub and it came out of the gloom and we saw it. It was one of those sights that put a shiver down your spine.

Coupled with the depth and the technicality of the dive and the years of searching just meant, we were hugely elated when we discovered it."

The whole operation was filmed and the documentary will air at Beau Sejour next month and on the BBC in June.

The site of the UC-18 remains secret between the small team who helped trace her and create the film. Because all the crew on board died, Karl says the site is a war grave and can no longer be dived on:

"There were 28 crew that were lost with the submarine and probably entombed in the silt inside. So we had a plaque engraved, and laid it with the names of the 28 submariners and left it that the submarine, chained around the gun."