Because they weren't used does not mean that they weren't required .
"Germany planned to use chemical and biological attacks during a wartime invasion of Britain, according to documents from the National Archives.
Aircraft adapted to spray gas or foot-and-mouth disease, and even anthrax shells, were seen as possibilities.
The Nazis were "rapidly preparing" by March 1941 and would not hesitate to attack, say the papers.
Gas attacks on troops were viewed as most likely, but attacks on the public were also predicted.
The newly-released documents - from the Ministry of Home Security and other bodies - say the aim would be to cause panic and start an evacuation that would block roads and prevent defending forces reaching the coast.
Intelligence also revealed that the Germans were planning to falsely accuse Britain of using gas in order to justify its own attacks.
The documents detail the ominous movement of large amounts of chemicals from factories to "areas occupied by troops likely to take part in an invasion".
It also lists evidence from various secret witnesses and "observers".
They include a Swedish army officer who saw gas canisters ready to be loaded at German air bases, and a prisoner of war who "had volunteered information that his squadron had carried out tests near Vienna of gas spray"."
https://www.bbc.co.uk/news/uk-13859049
It seems prewar British government was far more prepared for all eventualities than the government we have now.
The stockpile of medical equipment held in case of say a pandemic was almost totally depleted of PPE for getting on for a decade and even after constant warnings that it was a need for it to be replaced nothing was done though Dominic Cummings did ensure there were plenty of body bags available.