Cats were popular 9,500 years ago for their rat-catching skills, so it's probable that cat flaps are ancient. It is even thought that moggies were domesticated as long as 12,000 years ago. So we share something with our ancient ancestors – we all know the frustration of standing at the door, waiting for our feline friends to decide whether they’re coming in or not.
As for evidence, in Britain at least, cat flaps date back to the medieval era. In Geoffrey Chaucer’s The Miller’s Tale, a character drops to his knees to peek through a door: “An hole he foond, full owe upon a bord, Ther as the cat was wont in for to crepe”.
But if you want to see an old cat-hole up close, you can spot one a Chetham Library, in Manchester, built in 1421.
You can also visit Exeter Cathedral, where the clock tower was so bedevilled by mice chewing on the ropes that it possibly inspired the well-loved nursery rhyme Hickory, Dickory, Dock, the Mouse Ran Up the Clock. This charming tale is hard to prove, but the 17th-century cat flap in the tower door is very much real.