 The design was based on the British , but had all boilers grouped together reducing the number of funnels to two.The main armament comprised Vickers pattern 6-inch guns with single mountings in "A" and "Y" positions and twin turrets in "B", "Q" and "X" positions.The programme was initially authorised in 1915 but was delayed by World War I with construction of the first ship starting in 1917.