 935 (County of Glamorgan) Barrage Balloon Unit (Auxiliary Air Force), which was at Filton from January 1939 with 2 Flights of 8 barrage balloons, and responsible for the defence of the Naval Yard at Plymouth as well as the airfield at Filton.The unit's allocation was increased to 24 Balloons during August 1940 as RAF Filton did not have a defensive fighter squadron attached to defend the airfield.No.