The 1973 stock was built to provide new trains for the then new Heathrow Airport extension. The first ones were delivered on the 19th July 1975. OPO (One-Person Operation) was introduced on the 31st August 1987. CSDE (Correct Side Door Enable) equipment was introduced on 6th September 1993.

The trains underwent refurbishment at RFS of Doncaster from May 1993 onwards. New features such as perch seats and dot matrix indicators were fitted. Also pre-set digital voice announcements and inter-car barriers were incorporated in to the refurbished trains.

Interior of a refurbished 1973 stock train

Refurbishment plaque

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