It has been revealed that a shop which mistakenly undercharged a woman for blankets on ‘Decimal Day’ has been reimbursed – 38 years later.

The customer, aged 77, moved from Paignton, Devon to Berkshire in 1971 to take a new job and bought blankets for her unfurnished home.

When at the till, the assistant incorrectly calculated the conversion from pounds, shillings and pence to decimal, but the customer stayed quiet because she “was poor”.

“The girl did not have a clue how to work out my bill and I realised it was grossly in my favour. I felt guilty at the time, but I never said anything and kept it a secret because I was quite short of money and needed the blankets. It was an evil thing to do.”

Brian Carter, the department store's managing director, said he was “astounded” by the recent debt confession.

“I was the buyer in the actual department at the time, but I've absolutely no recollection of it," he said.

“Things were a bit chaotic that day, because all the goods had been re-marked in decimal and a lot of customers were asking what their goods cost 'in old money', so to speak. I think the only person who was aware of what had happened was [the customer] herself.”