"I rang up the county council and I said I think I've found a dinosaur," explained Joe Davis, who works at Rutland Water Nature Reserve.
During landscaping work at the reserve's reservoir in February 2021, he'd spotted something odd poking out of the mud.
They concluded it was an ichthyosaur - a type of warm-blooded, air-breathing sea predator not unlike dolphins. They could grow up to 25 metres long and lived between 250 million and 90 million years ago.
Dr Dean Lomax, a palaeontologist from Manchester University, was brought in to lead the excavation effort. He called the discovery "truly unprecedented" and - due to its size and completeness - "one of the greatest finds in British palaeontological history".
"Usually we think of ichthyosaurs and other marine reptiles being discovered along the Jurassic coast in Dorset or the Yorkshire coast, where many of them are exposed by the erosion of the cliffs. Here at an inland location is very unusual."
Rutland is more than thirty miles from the coast, but 200 million years ago higher sea levels meant it was covered by a shallow ocean.
When water levels at the Rutland reservoir were lowered again in the late summer of 2021, a team of palaeontologists came in to excavate the remains. Special attention was paid to the removal of the huge skull.
The block, weighing almost a tonne, was raised out of the mud and will now be examined further.
"It's not often you are responsible for safely lifting a very important but very fragile fossil weighing that much," said Nigel Larkin, palaeontological conservator and Visiting Research Fellow at Reading University. "It is a responsibility, but I love a challenge."
Anglian Water, which manages the Rutland reservoir, is now looking for funding to enable the ichthyosaur to stay in the area and be enjoyed by the general public.
"A lot of people thought I was pulling their leg when I told them I'd found a large marine reptile at work," Mr Davis said. "I think a lot of people won't believe it until the TV programme goes out."
That TV programme is on Tuesday 11 January at 8pm on BBC Two. "Digging for Britain" will then be available on the BBC iPlayer.