There were in 1940 onwards about 200 converted tar sprayers held at Randle. These were to spray the roads inland of any invasion beaches with mustard gas.
There were also a number of glass ampoules of mustard gas which were intended to be buried shallowly on roads. When German vehicles drove over them the persistent gas would have been released.
The major anti-invasion chemical warfare effort would have been the bombing our own beaches by the RAF. The attached link is to the planning document dated 1941.
We were very serious about resisting invasion.
http://i472.photobucket.com/albums/r...g?t=1242597173