Most of the diesel locos built up until about 1962 had end gangways, including classes 24, 25, 26, 27, 31, 37, 40, 44 and 45 plus the LMS twins, the original Southern diesel and the Metrovick Co-Bo (probably not a definitive list!). Where the loco also had a 4-character headcode display this was placed above the cab windows or split with 2 characters each side of the gangway. The gangways were supposed to be used for the crew to get between the loco and the train or between double-headed locos, although their tops were lower than the ones fitted to coaches. They were virtually never used.
After that date the gangways were no longer fitted to new production, including later runs of many of the above classes, and those that previously had split headcodes were re-designed with a 4-character display centrally on the nose. Many of the existing gangways were removed and the doors welded shut or plated over.
Although i am sure I have seen a chemical toilet on one type of train
