The father of a friend of mine flew Handley Page Hampdens in the early part of the war. Although it had four crew, the pilot was on his own up in the cockpit and couldn't move from there during flight. His pee tube went back through the fuselage and was accessable by the other crew members. Pilots had to be sure not to upset anybody because a blocked tube, or one with a knot tied in it, meant an uncomfortable overflow and spillage at the "business" end.