It was developed because of the foresight of Nottingham City Police Chief Constable Captain Athelstan Popkess.
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 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.
Firefighters successfully tackled a fire in the south transept at St Mary's Church after an incendiary bomb burned through the roof.
The vicar of St. Mary's, Neville Stuart Talbot noted: We had a visitation - nothing compared with some places, but still a very real taste.