Penrhos Works began producing aluminium in 1971 and has a capacity of some 126,000 tonnes per year. Alumina and coke ships berth at the jetty in Holyhead Harbour (NPRN 415517) which is linked by a series of underground conveyor belts to the plant. The plant is also served by a railway siding from the adjacent north Wales main line and this is used for receipt of raw materials and despatch of aluminium. A 132kv electricity line supplies power via the National Grid from Wylfa Nuclear Power Station (NPRN 306329). The stack is a prominent landmark at 122 metres high. 

B.A.Malaws, RCAHMW, 29 April 2008.

Detailed recording by the Royal Commission was undertaken prior to closure of the works, both through ground and interior photography of the process, and on 13th January 2012, from the air resulting in stereo oblique recording of the main building complex.

T. Driver, RCAHMW, 2013.

Smelting finished at the site in 2009 and Orthios Group acquired the site in 2016 in an attempt to create a biomass power station. This proved unsuccessful and in its place, a material recycling facility was developed but in March 2022 the group went into administration.

M. Powel, RCAHMW. October 2023.

Source: 'Anglesey: Orthios eco park workers told jobs lost at 'last minute'', BBC News, 30 March 2022; 'Reports show scale of debts Orthios group left after collapse', Business Live, 25 May 2022.