King Henry I was said to have been very fond of grilled lamprey
With its long slithery body, and a funnel-like toothed mouth, the lamprey sounds like a creature from some sort of horror movie.
But in reality, this rare eel-type creature is living in Lincolnshire's rivers.
Its numbers are thought to be on the up in the UK because the river-water is getting cleaner here.
The lamprey was once extinct in UK rivers, but is now having a resurgence, which is good news for our waters.
The river lamprey is one of three species of lamprey we can find here in Lincolnshire, alongside the brook lamprey and sea lamprey.
Lampreys have a circular mouth with rasp like teeth that acts as a suction cup
They can attach themselves to the skin of larger animals
Lampreys feed on the blood, body fluids and musculature of fish
Lampreys themselves can grow to about the size of a man's arm
The lamprey is a fairly ugly looking fish. It has no jaw, instead it has a single 'sucker' and the fish has no bones.
The river lamprey is the one which medieval royalty used to like to eat, probably because it was easy to prepare for the table. King Henry I was reported to have died from a surfeit of lampreys.
Brook lamprey can be found in most upland rivers in Lincolnshire. River lamprey spend a lot of time living in the River Lymn estuary, they then move upstream to spawn.
The Environment Agency are looking at putting a special structure in place in the weir at Partney Bridge, so the lampreys can migrate further upstream and complete their lifecycle much easier.
Sea and river lamprey are parasitic in their feeding habits. The sea lamprey latches on to fish like cod and can cause a lot of trauma to the fish. River lampreys also feed on the sides of fish like herring and sprat.
Lampreys need fresh-water to spawn and so improvements in water quality has increased their numbers.