its aluminium smelter, located on the outskirts of holyhead, was one of the largest employers in north wales, with 540 staff members, and began to produce aluminium in 1971. it was built on the penrhos estate, 500 acres of which were sold by the stanley family for the project. up until its closure it produced up to 142,000 tonnes of aluminium every year and was the biggest single user of electricity (255 mw) in the united kingdom.