but in 1941, the Italian navy successfully entered the harbor of Alexandria and damaged the two British battleships and , as well as the tanker Sagona. This feat encouraged the British to develop their own torpedo "chariots". The last Italian model, the SSB (for Siluro San Bartolomeo, "San Bartolomeo Torpedo") was built with a partly enclosed cockpit, a more powerful motor and larger warhead (up from the earlier SLC's warheads). Three units were made but not operationally used because Italy surrendered in 1943. The first British version of the concept was named the Chariot manned torpedo. Two models were made; Mark I was long while Mark II was long, both suitable for carrying two men. Later versions were larger, starting with the original X-class submarine, a midget submarine, long, no longer truly a human torpedo but, similar in concept. The X-Class were capable of on the surface or submerged. They were designed to be towed to their intended area of operations by a full-size 'mother' submarine. The German navy also developed a manned torpedo by 1943, the Neger, intended for one man, with a top speed of and carrying one torpedo; the frequent technical problems often resulted in the deaths of operators. Roughly 200 of these were made and they did manage to sink a few ships. The later Marder (pine marten in English) was about long and more sophisticated and could dive to depths of but with very limited endurance. About 500 were built. Construction A typical manned torpedo has a propeller, hydroplanes, a vertical rudder and a control panel with controls for its front rider. It usually allows for two riders who sit facing forwards. It has navigation aids such as a compass, and nowadays modern aids such as sonar and GPS positioning and modulated ultrasound communications gear. It may have an air (or other breathing gas) supply so its riders do not have to drain their own apparatus while they are riding it. In some the riders' seats are enclosed; in others the seats are open at the sides as in sitting astride a horse. The seat design includes room for the riders' swimfins (if used). There are flotation tanks (typically four: left fore, right fore, left aft, right aft), which can be flooded or blown empty to adjust buoyancy and attitude. Timeline 1909: The British designer Commander Godfrey Herbert received a patent for a manned torpedo.