Following the outbreak of war with France, the demands of the garrison, coupled with the difficulty of accommodating new steam-powered machinery, led at last to a decision to leave the confines of the Tower. The site chosen for the new Royal Mint was on Little Tower Hill, in an area recently occupied by tobacco warehouses and much earlier by the great Cistercian abbey of St Mary of Graces. Preliminary work began in 1805, the buildings were finished by the end of 1809, and the new steam-powered machinery was given a trial run in April 1810. During 1811 the transfer from the Tower was largely completed, though it was August 1812 before the keys of the old mint were finally delivered to the Constable of the Tower.
The new mint, with its ‘stupendous and beautiful machinery’, stood in sharp contrast to the old. The main building, designed by James Johnson and completed by Robert Smirke, achieved a ‘modest grandeur’. It was flanked by two gatehouses while behind it, and separated from it by an open quadrangle, were the buildings housing the machinery. There were dwelling houses for officers and staff, and the site was surrounded by a boundary wall, along the inside of which ran a narrow alley. Patrolled by soldiers from the Royal Mint’s military guard, this alley became known as the Military Way.
In the 1880s the factory buildings were reconstructed and extended, with new coining presses being installed and melting and rolling capacity increased. Further rebuilding was undertaken at the turn of the century; steam gave way to electricity; dwellings were taken over; and the work of construction and renovation became a continuous process as the Royal Mint endeavoured to cope with an enormous increase in the demand for coin at home and overseas. By the 1960s little of the original mint remained apart from the dignified Smirke building and its gatehouses in the front.