The results of experience gained with D1, the prototype diesel-driven submarine, were incorporated in the design of the famous E Class submarines, which did such outstanding work during the First World War.
The boats were considerably larger than the D Class, to accommodate the introduction of broadside torpedo tubes, a major change in the design. Six of the later E boats were fitted as minelayers. This meant that the broadside torpedo tubes were omitted and 20 mines were carried in vertical tubes in the saddle tanks. The mines were released by a mechanism operated from inboard.
The E Class were the first British boats to be fitted with internal watertight bulkheads. These internal bulkheads strengthened the
