In the 1950s and 1960s the view increasingly gained ground that it would be desirable to build an entirely new mint on a larger site. Matters were brought to a head by the government's decision, announced in 1966, to adopt a decimal system of currency. The task of striking hundreds of millions of decimal coins in readiness for decimalisation on 15 February 1971, while at the same time not neglecting overseas customers, made the construction of a new mint essential.
In April 1967 it was announced that the new Royal Mint would be built at Llantrisant in South Wales. A few months later work began on the construction of two large concrete-clad buildings, one for the treatment of blanks and the other for the striking of those blanks. This first phase was opened by the Queen on 17 December 1968, when she switched on the coining presses to begin production of decimal bronze coins.
After the decimal change-over had been successfully negotiated, a second phase of building work was undertaken at Llantrisant. Its main feature was a large melting, rolling and blanking unit, in which was installed one of the most up-to-date foundries in the world. Another substantial building provided accommodation for the Engraving, Tool-making and Assay Departments and for the special section responsible for the striking of proof coins for sale to collectors.
Once the Llantrisant facility was capable of the full range of minting activities, the Tower Hill site was quickly run down. The last coin, a gold sovereign, was struck at Tower Hill in November 1975 and the buildings were finally relinquished in 1980.