A 16th-century Scottish castle noted for its impressive defences has proved to be no match for a "very angry badger".

Craignethan Castle in South Lanarkshire, south-east of Glasgow, was breached by the nocturnal mammal on Saturday, forcing staff to close the stronghold's cellar tunnel to the public.

Castle staff tried to lure the badger out with cat food. ( By Kallerna/Wikimedia Commons. )

"We're trying to entice it out with cat food [and] send it home," Historic Scotland tweeted.

It is believed the badger has since retreated from the tunnel.

"Our works team have used a Go Pro this morning to view the tunnel and it seems our visitor has vacated."

"We'll keep the tunnel closed in the interim while we do a little housekeeping following its visit."

According to Historic Environment Scotland, Craignethan Castle is the last great private stronghold built in Scotland.

Badgers are a protected species in the United Kingdom and cannot be wilfully killed, injured or taken.

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Their burrows, also known as setts, are also protected.

Badgers are described by the Scottish Wildlife Trust as one of Scotland's "most charismatic mammals".

Badger takes cat nap

Craignethan Castle was not the first time a badger has found itself under the wrong roof.

In October, Scotland's Animal Welfare Charity was called to a home in Linlithgow, west of Edinburgh, after a badger snuck in through a cat flap.

Animal Rescue officer Connie O'Neil said the badger ate all the cat food before going for a sleep on the cat bed.

"I got a surprise when I arrived at the property and saw a badger having a nap," Ms O'Neil said.

"He didn't seem too happy when I tried to move him but I was able to slide the cat bed round and it was then that the badger noticed the back door was open so made a run for it."

Scottish SPCA chief superintendent Mike Flynn said it was highly unusual for a wild badger to enter a house and urged people not to go near them as they could be aggressive when injured or cornered.