British War Cabinet approved building of 18 H-class submarines on 26 June 1917

An item reported that the War Cabinet on Tuesday 26 June 1917 considered proposals (Paper GT.-1133) done by the Board of the Admiralty dealing with an increased programme to be completed by the end of 1918 als regarded War Cabinet No. 58. Factors as the expected strength of the German navy, the need for destroyers for anti submarine warfare and no disturbing of the merchant shipbuilding resulted in the War Cabinet approving the laying down of 18 H-class submarines of which 8 instead of earlier approved 4 L-class submarines. Furthermore was the Admiralty allowed to exchange already approved L-class boats for H-class.

Source

The National Archives, Kew Gardens, England CAB 37-23-3-17