The W class submarines were built for the Royal Navy as experimental boats. They were based on a French Schneider-Laubeuf design. The design for W3 and W4 was heavily modified to meet Royal Navy requirements, overcoming some of the deficiencies of the 'off the shelf' design. In particular, the drop-collars were removed in the later boats. Only 4 W class were built from 1913 to 1916. The first 2 boats took 15 and 17 months to build which at the time was a remarkable feat compared to other building times.