This was the worst air raid since early January, but was not on the scale of many last year. London was at alert from 1948 to 0003. All groups and 55 local authorities were affected, but the main weight of attack fell on the centre of London. HE’s were mixed with IB’s from the beginning of the raid, and although many IB’s (some stated to be of a new type – see below)* were dropped, fire raising did not appear to be the first object of the raid. IB’s were put out very quickly and only two fires required more than 10 pumps. All were under control by midnight.
She sank deeper and deeper, the indicator hand of the depth gauge showed an increasing depth down to 200 metres (656 ft.), the deepest limit marked, and then went on until stopped by the check. Ominous cracking sounds were heard, the paint flaked off the sides, and the crew thought that the hull would be crushed by the tremendous pressure of water. The supply of compressed air was by that time reduced to 25 kilograms; this was used in a last attempt to rise; the U-boat had gone down by the stern, and was now at an angle of 45 degrees.