People have said their “minds are blown” after finding out what the intricate patterns on custard creams actually are. The popular treats, which are thought to have originated in the UK back in 1908, are known for their signature stamped top layer.

While many of us have indulged in a custard cream or two over the years, few of us have likely wondered why they have their unique baroque design.

But now a history expert who works at the Manchester Museum has explained all. In a video posted to the museum’s official Instagram account, Bryony said: “Between the 1840s and 1890s in the UK there was a craze that was bigger than Pokémon cards. It was called the fern madness, Pteridomania.

“When trains and the train lines started to come to the UK, going to remote places became fashionable and so people would try and find things that were in those remote, cold places, things like ferns. It became a symbol of friendship, of good times, and intelligence of course.”

“And that’s why you see fern patterns on things like Victorian architecture, on birthday cards, and also the pattern on custard creams. They’re some ferns unfurling.”

People have been quick to react in the comments section, with one follower saying: “Fascinating! I always thought it was some design overhang from the art nouveau period.” A second said: “Mind blown, had no idea but this is fascinating”.

Custard cream enthusiasts may also find it interesting that the biscuits were made with custard powder rather than egg. Custard powder was invented by Alfred Bird, because his wife was allergic to eggs.

Food historian and author Lizzie Collingham described the fusion of custard with biscuits as ground-breaking, saying: “It was seen as a modern, exciting thing to make a food. Biscuits were the first industrial food, the first foodstuff to be produced by a machine; from mixing, kneading, rolling out, cutting out, baking, it could all be done with minimal intervention from people.

“To put custard powder in a biscuit… it brought together two things which represented industrial progress.”