The black rat, also known as the old English rat or ships' rat, was the only rat in England until the 18th century, when it was ousted by its aggressive cousin, the brown rat.

Apart from the occasional sighting in dockyards, the rat has been absent from the UK for up to 100 years - until pest controller Spencer Rickard found six of the rodents in the Cornish areas of Mylor and Truro.

Mr Rickard said: "I didn't believe the lady (who called me out) when she said they were black rats because I had never seen one, but when I saw them I knew what they were.

"The latest one was under a fridge. I got it and killed it and brought it back to the office and we took measurements of it. It was definitely 100% a black rat.

"It looks completely different. I call it the model rat. It is slim, the feet and skull are different and the fur is like velvet.

Black rats are notorious for carrying fleas, which are widely thought to have been responsible for bringing bubonic plague to Britain.

"We did check it for fleas", said Mr Rickard, " but there weren't any."

No need for alarm

"I've been catching rats for 20 years and I'm just pleased to have seen a black rat because they aren't supposed to be here," Mr Rickard said. "You only find them in a couple of places in the country at docks."

Stella Turk of the Cornwall Wildlife Trust examined the most recent corpse.

"The skull was damaged but as far as I can tell there is a high probability it was a black rat," she said.

Mr Rickard said the rats could breed quickly and it was likely there were more of them.

"I do believe in all probability there are more of them because this one was five miles inland," he said.