 Two single 18-inch (450 mm) torpedo tubes were fitted under the bridge on single rotating mounts port and starboard, intended to be fired directly by the commanding officer with toggle ropes during night actions, and the searchlight was relocated aft, mounted on top of the aft torpedo tubes (this to avoid the bridge officers being blinded by its glare during night actions).The single 18-inch torpedo tubes proved to be of little use, and were soon removed in the majority of vessels as a weight-saving measure (only "Tara", "Tintagel", and "Trojan" retained theirs).The S class was built in two batches, the first 33 ordered on 9 April 1917 and the second batch of 36 in June 1917, respectively.