109 Sqn was formed in November 1917 but was disbanded 9 months later without becoming operational. It reformed at the end of 1940 and was used special operations identifying ways of jamming German radio and radar signals. It flew a variety of aircraft and had one Lancaster for a couple of months before converting totally to the Mosquito. Post war it replaced the Mosquito with the Canberra which it operated until 1957 when the squadron disbanded.