King Charles was presented with the first editions of the new £5, £10, £20 and £50 banknotes featuring his portrait today at Buckingham Palace.
It was a milestone moment for the monarch, who is undergoing treatment for an undisclosed cancer, and marks one of the last major steps of his transition to King, with new stamps and coins already in circulation.
The Governor of the Bank of England Andrew Bailey presented the King with a leather-bound booklet containing the first edition historic legal tender.
King Charles III (left) is presented with the first bank notes featuring his portrait from the Bank of England Governor Andrew Bailey at Buckingham Palace
The King and Mr Bailey were joined by Sarah John (right), the Bank of England's Chief Cashier, whose signature appears on the currency
A view of the £5 and £10 bank notes bearing a portrait of King Charles III, which will enter circulation on June 5
The other side of the bank notes will remain the same as they were previously. The other side of the £5 and £10 bank notes can be seen on the left, while the £20 and £50 notes bearing the King's face can be seen on the right
It follows tradition for the monarch to receive the first issues of new banknotes with 01 000001 serial numbers.
King Charles is only the second British monarch to grace the Bank of England's notes, making it the first time one sovereign's image has been replaced with another.
The King praised the notes, that launch on June 5, as 'very well designed' and expressed his surprise at being only the second monarch to feature.
A £5 bank note bearing a portraitof King Charles III, which will enter circulation on June 5
One subtle difference some may not notice is that unlike the late Queen in the banknotes from her reign (pictured), King Charles is not wearing a crown.
An old £1 banknote from the 1940's featuring Britannia, the national personification of Britain, before it was swapped for Queen Elizabeth's portrait in 1956
He said: 'This is what is so surprising. You would think that it goes back'.
Although notes began to be issued from the late 17th century, Charles's mother, Queen Elizabeth II, was the first British sovereign to be given the honour in 1960 on a £1 paper note. Before this, Britannia was the only character to have appeared.
The engraving of King Charles on the new polymer notes is based on a picture taken in 2013.
One subtle difference some may not notice is that unlike the late Queen in the banknotes from her reign, King Charles is not wearing a crown.
The King and Mr Bailey were joined by Sarah John, the Bank of England's Chief Cashier, whose signature appears on the currency.
The King inspected the notes and praised the intricate features incorporated to prevent counterfeits, saying: 'A lot trouble taken in on the security side.'
The money will be issued gradually into circulation from June 5 - with Charles's portrait featuring on the front of the banknotes, as well as in cameo in the see-through security window, visible on the front and back.
The reverse side characters remain unchanged from previous editions - with Sir Winston Churchill on the £5, Jane Austen on the £10, JMW Turner on the £20 and Alan Turing on the £50.
Charles expressed his admiration of the artistry, saying of the £5: 'It's a very good photograph of Sir Winston.'
Existing notes featuring the portrait of the late Queen will continue to be legal tender, so the Elizabeth II and King Charles III notes will co-circulate.
New notes will only be printed to replace worn-out ones and to meet any overall increase in demand in order to minimise the environmental and financial impact of the change - in keeping with the Royal Household's request.
This gradual change coupled with a general public leaning towards cashless payments means that it could be months after the new notes launch on June 5 that some people even see them in circulation.
The Bank of England began printing the new banknotes last year to give enough time for automated machines that accept cash to be updated to recognise the new tender.