Re-armament programmes during 1936 recognised the value of magnesium metal for lightweight alloy and incendiary bomb production. The Air Ministry instructed Magnesium Elektron of Manchester to increase their capacity from 1500 tons to 4000 tons per annum. Before producing this extra tonnage it became obvious that if war ensued, the sources of natural magnesite (the process raw material) might no longer be available. A similar situation had impacted upon steel production during WWI. The UK has no natural magnesite and a home source of magnesium oxide was needed. Co-operation with the British Periclase Company of Hartlepool started mid 1938 to produced a reactive magnesia suitable for metal manufacture. During February 1939, as a result of their efforts, magnesium metal was first produced at Clifton Junction from magnesia extracted by British Periclase from dolomite and sea-water.

Early in the war it became apparent the demand for magnesium called for a further rapid expansion at Manchester and a significant increase in tonnages produced by the sea-water process. Magnesium Elektron added a second and larger plant at Clifton Junction.

Magnesium flare about to be dropped

At government request the British Periclase Company designed and built a second plant at Harrington, near Workington, on the Cumberland coast, exclusively for the production of  reactive magnesia for processing into magnesium metal – vital for the light alloys used in aircraft frames and for munitions. The powdered magnesia was transported to Clifton Junction at Manchester for further processing by Magnesium Elektron Ltd.

Wellington bomber assembly

Initial excavations started on the 3rd July 1940 and construction work was completed during 1941 after only 12 months (by some 1500 construction workers). Harrington shore Works, sometimes referred to as the Ocean Salt Works had a capacity of 40,000 tons per year of magnesia and Hartlepool 16,000 tons.When completed both works passed into government ownership - Hartlepool remained under the control of the Ministry of Supply and Harrington under the Ministry of Aircraft Production.