Operation Sandcastle

Operation Sandcastle was a British Ministry of Defence operation conducted in 1955-56 to dispose of chemical weapons at sea. It was the third of four 'phases' to dispose of unwanted chemical ordnance by the British government.

The British possessed almost 71,000 250 kg bombs filled with tabun. These had been seized from German ammunition dumps in the final months of World War II. A total of 250,000 tons of chemical weapons had been uncovered, the majority were destroyed but stocks of tabun and sarin were divided between Britain and the United States after discussion, with the Americans taking the sarin. The British transferred their 14,000 tons of ordnance in October 1945, via Hamburg and Newport, to temporary storage at the RAF strategic reserve ammunition store at Llanberis. Longer term facilities were prepared at RAF Llandwrog, the bombs were to be stored in stacks in the open on the runways of the disused airfield - any leaks would be carried out to sea by prevailing winds. The bombs were taken to Llandwrog by truck from August 1946 to July 1947.

In July 1947 it was discovered that the bombs were fuzed and that a number were leaking. At a rate of 500 bombs a week they were defuzed and individually coated in a waxy preservative to seal them. Seventy-two irreparable devices were neutralised on-site by being drained into individual pits filled with caustic soda crystals. Despite the preservative the bombs continued to suffer in the damp Welsh climate and in 1951 twenty-one 'Bellman' hangars were erected on the site to store the bombs. Finally in June 1954 it was decided to dispose of the entire stock as it was, by then, clearly of no military value.