On 21st September 1940 Air Raid Warning Purple was received at 01:36 hrs. At 01:25 hrs a single enemy plane was heard over the town. First information began to be received at 03:35 hrs with reports of unusually heavy detonations. It was thought at first an enemy plane had crashed but it was soon established that two parachute mines had been dropped.
The first landed in a Monumental Stonemason’s yard about half a mile from the town center, but did not fully explode, with the major portion of the body of the mine lying exposed with its parachute still attached.
The second landed one and a half miles distant, towards the Borough boundary on the north east side of the town. This exploded properly and left a crater about five feet deep and 20 feet in diameter. Wardens from Post A3, Windyridge, Woodbridge Road East, were soon on the scene, one warden even making his way to Post A3 in pajamas and dressing gown to make his report. Wardens and a Special Constable made a house to house search. A couple trapped in their Anderson Shelter by debris were freed. Injuries were limited to cuts from flying glass and a Sitting Case car was summoned for one man who was badly cut. A fire in a garage was promptly dealt with by the Auxiliary Fire Service.
A house 50 yards away was virtually demolished. A housing estate lay within 200 yards of the explosion and damage within 200 yards was server with a lighter zone of damage up to 500 yards distant. Damage was mainly to roofs, windows and some overhead cable and telephone wires. According to the Chief Warden, damage was: