No. 152 (Hyderabad) Squadron RAF were a very experienced unit, having been flying Spitfires since they were on the front line of the Battle of Britain. They had then seen service in North Africa and Sicily. In December 1943 they transferred to India where they would soon be taking an active role in the campaign in Burma.
There were nearly 2000 in the shelter, including several hundred who had arrived after the Alert, when a middle-aged woman, burdened with a bundle and a baby, tripped near the foot of a flight of 19 steps which leads down from the street. This flight of steps terminates on a landing. Her fall tripped an elderly man behind her and he fell similarly. Their bodies again tripped up those behind them, and within a few seconds a large number were lying on the lower steps and the landing, completely blocking the stairway.