Most Brits will be familiar with the UK’s four different banknotes, even in an increasingly cashless society. Yet many have been surprised to find out one detail about the notes shared by a Reddit user recently.

Banknotes in the UK have undergone some changes recently, most notably the shift from portraits of the late Queen Elizabeth II to the current monarch, Charles III. But one keen Reddit user has noticed the height of each banknote is around half the width of the next largest note. So the width of two £20 notes, for example, measures exactly the same as the length of a £50 note. The pattern is slightly off as the denominations decline in size, with the width of two £10 notes measuring 1mm short of the length of a £20 note, and two £5 notes having a combined width 2mm short of a £10 note’s length. Other Reddit users sent quips in response to the “experiment”, with one saying: “Look at money bags here.”

Another said: “Now that the research has concluded, can you send me the research equipment please.”

Notes featuring the King’s portrait were first issued in June last year by the Bank of England, while the various different denominations have been updated in the last decade to change the faces displayed and move to a more durable plastic note.

For instance, the £5 in its current form was first issued in September 2016 and features wartime prime minister Sir Winston Churchill.

It also has a hologram, which changes from reading “Five” to “Pounds” when the note is tilted, while its border shifts from purple to green when the note is moved.

The £5 note also features the Churchill quote from his first prime ministerial speech: “I have nothing to offer but blood, toil, tears and sweat.”

Featuring author Jane Austen, the current £10 note was issued in 2017, featuring her quote: “I declare after all there is no enjoyment like reading!”

Artist JMW Turner, who gives his name to the art prize and the “Turner View” from Richmond Hill, is featured on the £20, issued first in 2020.

His “The Fighting Temeraire” is featured on the note, one of his most famous paintings done as a tribute to the HMS Temeraire, which played a distinguished role in Admiral Lord Nelson’s victory at the Battle of Trafalgar in 1805.

Scientist Alan Turing completes the set with his feature on the £50 note, first issued in 2021.

Turing provided the theoretical underpinnings for the modern computer and is best known for his work devising code-breaking machines during the Second World War.

He was convicted of gross indecency for his relationship with a man but was posthumously pardoned by Queen Elizabeth II.

All notes feature a “cluster” of raised dots in the top left hand corner to aid blind and partially sighted people identify the value of the note, though the size of notes can also help to distinguish between them.