In the early years of the war, they saw action defending shipping against enemy torpedo boats such as the German E-boats on the southern and eastern coasts of the UK. MGBs were also involved in the protection of shipping after D-Day. They did not take the prefix HMS as they were only boats and instead used the prefix "HMMGB" on formal occasions. The crews generally referred to them by their numbers. In 1947, MGB 2009 was fitted with a Metrovick gas turbine, thereby becoming the world's first gas turbine powered naval vessel.