AT the outbreak of the war, the chief employer in Northwich was Brunner Mond, which ran several works across town.

In 1916, the company acquired the Ammonia Soda Company Ltd’s works in Plumley – then Plumbley – off Ascol Drive, so named after the company.

The works had been built after brine was discovered on the Holford Hall Estate, and were constructed off what is now the A556, just before Lostock Gralam and near the Mid Cheshire Line railway.

After Brunner Mond moved in, and on the direction of the Ministry of Defence, the factory began producing and stockpiling ammonium nitrate for use in munitions.

The Historic England ‘scheduled monument’ entry for the site explained that demand for explosives led to chemical developments, allowing mass production in Britain’s unpredictable temperatures as never before.

The entry said: “An alternative was to use sodium nitrate and calcium chloride to create calcium nitrate. This could then be treated with ammonia (in which Britain was rich) and carbonic acid to give ammonium nitrate.

“An experimental plant to produce calcium nitrate was established in 1915 at Plumley, which had come under the control of the Ministry of Munitions.

“This was quickly followed, beginning in 1916, by large-scale production, which was also established at the Salt Union’s Victoria Works near Northwich.

“After the First World War, Lord Moulton, Director-General of Explosives Supply in the Ministry of Munitions, wrote to Brunner Mond’s chairman: 'We have been indebted to your Company for the manufacture of the bulk of the largest component of the high explosives used by this country in the war’.

“In total 216,120 tons of ammonium nitrate were made during the war – almost 90 per cent of it by Brunner Mond.

“The calcium nitrate process was used to create just under 60 per cent of the national ammonium nitrate output.

“The Plumley works manufactured 43 per cent of the calcium nitrate used, and thus directly provided vital ingredients for 25 per cent of all the ammonium nitrate used by this country to manufacture high explosives for the war.”

Although most of the buildings on the site have since been demolished, one huge, reinforced brick warehouse remains standing.

It is currently subject to a planning application for conversion into eight townhouses.