P FLAG SUPERIOR NUMBERS WERE ALLOCATED TO ALL SUBMARINES CONSTRUCTED DURING THE WAR. U CLASS SUBMARINES - MOST WERE RENAMED WITH NAMES PREFIXED BY “U” FROM FEB 1943, SEE NEXT LIST.UNTIL THE SECOND WORLD WAR, IT WAS USUAL FOR SUBMARINES TO HAVE ONLY A PENNANT NUMBER AND NO NAME; WINSTON CHURCHILL DIRECTED THAT ALL SUBMARINES BE NAMED.