 The John Player & Sons tobacco company had built a network of tunnels at its factory and under local streets sufficient to house around 5,000 of its workers.The raid on the night of 8–9 May by the "Luftwaffe" was targeted at Nottingham and Derby.The X-Gerät beams set up to cover the Rolls Royce works were detected, and radio counter-measures diverted the attack to the moors north east of the town.