Instead, she walked away with a receipt claiming her remaining balance was a staggering £63 quadrillion. The astronomical figure made her, quite literally on paper, the wealthiest person on the planet.

The confusion began at the till when staff noticed a peculiarity in the transaction, with one barista admitting they had never seen such a balance before. According to a spokesperson for the coffee chain, the error occurred because the gift card’s identification number was accidentally entered into the balance field of the software. While the printed receipt served as a humorous souvenir of her brief status as a quadrillionaire, the shop’s system maintained the actual value of the card, and a second, corrected receipt was issued to reflect the true remaining funds, BBC reports.

Despite her newfound digital fortune, Ms Downing remained grounded. She jokingly noted that she would have preferred such a balance at a supermarket, but she chose not to exploit the glitch, opting only to treat herself to one additional drink.

She remains content to enjoy the novelty of the mistake while it lasts, having shared the hilarious encounter with her partner and kept the receipt as a memento of the world’s most expensive mistake that cost her nothing.