Maintenance Unit No. 81 is situated near Barnard Castle in County Durham. This site stored weapons charged with mustard, phosgene and lewisite on an area of 564 acres of moorland. In total 17,000 tonnes of chemical agent was stored on the site during WWII.
After the Allied retreat from Dunkirk in 1940, chemical weapons were returned from the continent and a remote open site on moorland in the north of England should be found for the establishment of an open air CW reserve depot.
The move of RAF bombs to Bowes Moor began in December 1941
In the first year sheep were let freely graze amongst the munitions. They quickly consumed the tarpaulins covering 65Lbs liquid chemical bombs and then attempted to eat the shell/bombs themselves, puncturing many of the thin cased shells much to their-the sheep and the bombs-ultimate disadvantage. Later on the soldiers erected many miles of sheep proof fencing and gates.
Today there are still parts of the site fenced off from the public due to contamination, yet the sheep still graze the site.