With reference to automatic warning systems for track workers (NCE 15 March), a simple and effective replacement for the 'flag and horn' was developed in the LMR of BR in the 1970s.
It consisted of (i) a portable lookout operated system which allowed an advance lookout man to be positioned so as to give the gang a minimum of 25 seconds warning of trains via cable to a sounder or to plug in to the lineside track circuit cables at the worksite, (PEEWEE), and (ii) a fixed system actuated by track circuits to operate sounders, initially YODALARMS, located along the lines to be protected (FATCOWS).
Many sets of PEEWEEs were brought into use and several FATCOWS were installed - they may be heard yodelling on the East Coast Main Line to this day.
Sadly, the system described by Colin Simpson was thought to offer better prospects and it seems that conceived to be best became the enemy of the good.
J McCulloch (M), One Briar Dene, Maidenhead, Berks SL6 6SF.