Birmingham’s aircraft shadow factories may have been in the Luftwaffe’s bombsights, but there was no serious interference to production. Why were its efforts so ineffective?

The sun would have been setting on their port beam as the first of 21 Heinkel He 111s crossed the French coast bound for Birmingham — in particular, for the Spitfire factory at Castle Bromwich and the nearby Dunlop plant. The bombers were split into sections of three aircraft each, and spaced at half-hourly intervals. Three different routings were to be used in the attack, so waves of aircraft arrived in the target area at different times and from varying directions. By way of an example, one Heinkel assigned to bomb Fort Dunlop, flying at 19,500ft, routed via Taunton, Swindon and Birmingham and, for the return trip, through Carmarthen and Brest.