of the other Zeppelins reached central London: bombs fell on Woolwich, Guildford, Tonbridge, Croydon, Hertford and an army camp near Folkestone. A total of 71 people were killed and 128 injured. This was the last raid of 1915, as bad weather coincided with the new moon in both November and December 1915 and continued into January 1916. Although these raids had no significant military impact, the psychological effect was considerable. The writer D. H. Lawrence described one raid in a letter to Lady Ottoline Morrell: 1916 The raids continued in 1916. In December 1915, additional P class Zeppelins and the first of the new Q class airships, were delivered. The Q class was an enlargement of the P class with improved ceiling and bomb-load. The Army took full control of ground defences in February 1916, and a variety of sub 4-inch (less than 102 mm) calibre guns were converted to anti-aircraft use. Searchlights were introduced, initially manned by police. By mid-1916, there were 271 anti-aircraft guns and 258 searchlights across England. Aerial defences against Zeppelins were divided between the RNAS and the Royal Flying Corps (RFC), with the Navy engaging enemy airships approaching the coast while the RFC took responsibility once the enemy had crossed the coastline. Initially the War Office had believed that the Zeppelins used a layer of inert gas to protect themselves from incendiary bullets, and favoured the use of bombs or devices like the Ranken dart. However, by mid-1916 an effective mixture of explosive, tracer and incendiary rounds had been developed. There were 23 airship raids in 1916, in which 125 tons of bombs were dropped, killing 293 people and injuring 691. The first raid of 1916 was carried out by the German Navy. Nine Zeppelins were sent to Liverpool on the night of 31 January – 1 February. A combination of poor weather and mechanical problems scattered them across the Midlands and several towns were bombed. A total of 61 people were reported killed and 101 injured by the raid. Despite ground fog, 22 aircraft took off to find the Zeppelins but none succeeded, and two pilots were killed when attempting to land. One airship, the L 19, came down in the North Sea because of engine failure and damage from Dutch ground-fire. Although the wreck stayed afloat for a while and was sighted by a British fishing trawler, the boat's crew refused to rescue