The W-class submarines were built for the Royal Navy as experimental boats.

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.

The W class had very good performance, with excellent diving control and efficient venting and flooding systems.

The class did have problems with habitability, but other than that, they were good submarines.

All four of the W-class submarine were transferred to the Italian Navy in August 1916, where they retained their numbering.