On 25 September 1940 all three air groups took part in a raid on the Bristol Aeroplane Company factory at Filton. German reconnaissance discovered the surrounding airspace was sparsely protected. A formation of 58 Heinkels supported by Junkers Ju 88s from "Lehrgeschwader" 1. A formation of Messerschmitt Bf 110s from "Erprobungsgruppe" 210 marked the target. RAF controllers mistakenly believed the target to be the Westland Whirlwind factory at Yeovil and sent three squadrons to protect it. This enabled the bombers to bomb the target, stopping production and causing some 250 casualties at the factory and 107 in the surrounding area. 80 Bristol Beaufort and Bristol Blenheims were destroyed and dozens of others damaged. RAF fighters from No. 238 Squadron RAF and No. 229 Squadron RAF engaged the He 111s on their return to base, downing one He 111 and two escorting Bf 110s from III./"Zerstörergeschwader" 26.