The Mint dates itself from 886, the year Alfred the Great struck pennies bearing his title Rex Anglorum - king of the English. There had been earlier coinages in Britain - Celtic imitations of Greek originals in the second century BC, Roman mints active in London and Camulodunum until the empire withdrew - but the institutional descent of the modern Royal Mint runs from the Anglo-Saxon coinage forward. In 1279 Edward I unified the country's many local mints under a single system based at the Tower of London, where the Mint would remain for almost six hundred years. Mint Street still runs along the line of the old Mint walls inside the Tower. Isaac Newton became Warden of the Mint in 1696 - a post intended as a sinecure for an aging genius - and turned it into an active campaign against counterfeiters, prosecuting them with the same patience he had brought to optics. Forgeries at the time accounted for roughly ten percent of the country's coins.

By the early nineteenth century the Mint had outgrown its medieval quarters. Construction began in 1805 on a purpose-built site at Tower Hill, just outside the Tower's western walls, designed by James Johnson and built by Robert Smirke. The keys of the old mint were ceremoniously handed to the Constable of the Tower in 1812. The Tower Hill mint coined for the British Empire at its greatest extent. Satellite mints opened in Sydney in 1855, Melbourne in 1872, Ottawa in 1908, Bombay briefly during the First World War, and Pretoria in 1923 - each producing local coinage to the same standards under licence from London. The Tower Hill site survived the Blitz, though three staff were killed in an air raid in December 1940. An auxiliary mint was set up at Pinewood Studios in Buckinghamshire, requisitioned from the film industry, which struck coins from 1941 until the war's end. The Mint at this period was producing roughly 700 million coins a year despite the bombs.

Decimal Day was set for 15 February 1971. The country needed billions of new coins to replace the pre-decimal coinage - shillings, sixpences, half-crowns - that had been struck for centuries. The cramped Tower Hill site could not do it. Over twenty alternative locations were considered, including sites in Scotland and Northern Ireland. The successful bid came from Llantrisant in Glamorgan, a small Welsh town on the road from Cardiff toward the western valleys. The reasons were partly political - the Welsh Office wanted heavy government investment in Wales to offset the decline of coal - and partly practical: the site was flat, well-served by road, close to the M4, and large enough to expand. Construction began in August 1967. The first phase, the blank treatment plant and striking floor, opened in December 1968 with Queen Elizabeth II and Prince Charles in attendance. Phase two, completed in 1973, added the melting and rolling facilities so the Mint could produce coins from raw metal. The final cost was eight million pounds. The last coin struck at Tower Hill, a gold sovereign, came off the press in November 1975. The Tower Hill buildings survive as office space; the Mint itself moved entirely to Wales.

The new Mint sits on a 38-acre site about ten miles northwest of Cardiff, accessible from junction 34 of the M4. From the road it looks much like any industrial estate - low brick buildings, security fences, lorries coming and going. Inside, the work is unlike any other in Britain. The Mint strikes coins for the United Kingdom and for sixty-odd overseas customers. It produces precious metal investment bars, commemorative coins, military medals, and the dies for British passport stamps. Each year it produces hundreds of millions of pieces of legal tender. Since 2018, with the cash economy in steady decline, the Mint has reinvented its business. A jewellery line called 886 - named for Alfred's date - launched in 2022 using gold reclaimed from electronic waste at a new processing plant in South Wales. The Mint's 2020-21 operating profit was 12.7 million pounds. Most of that came not from making circulating coins, but from selling precious-metal products to collectors and investors.

Every coin in the United Kingdom - every penny, every fifty-pence piece, every pound - was struck in Llantrisant. The country's small change is made on the western edge of the South Wales coalfield, on a site that thirty years before the Mint arrived was farmland. The new Mint has a visitor centre. Tourists can watch a coin being struck and take it home. The Welsh language appears on signage alongside English. Llantrisant itself, the town that gave its name to the operation, is a small place with a Norman castle ruin on a hillside and a market square that the new Mint did not change. Decimalisation, when it finally came in 1971, swept away the old pounds, shillings and pence on which generations of Britons had done sums in their heads. The coins that replaced them came from Llantrisant. They still do.