A routine inspection by staff at a power station in the Medway estuary, Kent, caused a bit of a shock.
Although they are used to seeing fish taken in with the water supply at Powergen's Kingsnorth station in Rochester, nothing prepared them for a 90cm/3' 'vampire' fish.
The sea lamprey - a tubular, eel-like fish with its two sets of sucker-teeth, one for holding on to bigger fish, the second for scratching and sucking their blood - have fossil records going back to the Carboniferous period, some 340 million years ago, and have remained virtually unchanged since then.
This is only the second sighting in south-east England, according to the Environment Agency.