The origin of the chariot is unclear but perhaps the first was used by Alexander the Great in the siege of Tyre (332 BC). Bushnell’s Turtle in 1776 was a bold attempt to attack ships with wooden hulls as can be seen by the sketch (page 41 of my book)
Inventors seemed to concentrate on small submarines until the first world war when the Italian navy supported Lieutenant Rossetti and Lieutenant Paolucci to adapt a torpedo that successfully blew up a battleship and encouraged the development of this craft before the Second World War by the Italian Navy.
One thing to bear in mind when modelling a chariot is that they varied slightly because as time passed adjustments were made to improve performance, propeller guards were added, streamlining took place and some carried two war heads.
Finally both the Italian and British Mark II designs were lengthened for the inclusion of a cockpit so only the operators head was visible above the hull line.
It should also be borne in mind that this craft would not work unless the operators were able to breathe underwater with a revolutionary breathing apparatus for its time that would not discharge bubbles and be easily spotted by sentries patrolling harbours.
A very crude and dangerous breathing set was produced using pure oxygen dangerous below 30 feet. These men were the forerunner of the modern frogman.
Prime Minister Winston Churchill saw the advantages of the Chariot and indeed encouraged the development of Underwater Warfare through the offices of the Special Operations Executive (S.O.E.). The SOE was formed in 1940 to engage in subversive activity but soon expanded its activities to use university students to invent devilish devices. At an old hotel in Welwyn Garden City the Sleeping Beauty, Welman and Welfreighter submarines were invented and built and then taken to a reservoir in Staines and Tested at the SOE’s secret base known as Station VIII. The Special Boat Service (S.B.S) was formed to take the responsibility the craft and missions that were launched from the sea. In 1946 the S.O.E was disbanded however those active groups formed under its wing continued to the present time.