In message , Paul Corfield
writes

Well theve got a long way to travel on the Central Line.

Technical officers are positioned at a number of locations on the
biggest lines to ensure a decent response time. Favourite locations are
often at the same places where LU drivers have their change over points
such as White City or Leytonstone or Arnos Grove or Wembley Park.

Ahem... Technical Officers are the blokes wot mend the signals. You're
thinking of (depending on the line), TT1, Train Technician, Fitter,
Train Doctor or Car Examiner.
--
Steve Fitzgerald has now left the building.
You will find him in London's Docklands, E16, UK
(please use the reply to address for email)