|Number built:||450 (75 6-car sets)|
|Engine:||Brush LT118 traction motors (630v DC third & fourth rail)|
|Formation:||Driving Motor (DM)+Trailer (T)+
Uncoupling Non-Driving Motor (UNDM)+UNDM+T+DM
(Some sets are DM+T+DM)
The D78 Stock cars were the longest on the Underground, which proved to be a problem on the District Line's High Street Kensington - Edgware Road branch as the D78 Stock was too long (C Stock trains were used instead)!  Most D78 Stock formations had 2 Driving Motors (DMs) at either end with non-driving motor cars in the middle, though some had DMs in the middle meaning they could be used as 3 car sets. They were used as such for a couple of years on the East London Line in the mid-1980s.
The D78 Stock fleet received a heavy mid-life refurbishment in the 2000s but were replaced as part of London Underground's standardisation for its Surface Stock fleet. The D78 Stock's replacement by S Stock was complete in Spring 2017, a number of years earlier than planned. Its possible the D78 Stock could live on on the National Rail network as Class 230 DMUs (or bi-mode hybrids), development is continuing.
|7535 at West Brompton|
|7094 at Earls Court|
|7049 at Kew Gardens|
|Aboard a D Stock train in its latter days|
 Paul Moss, London Underground 1863 Onwards (Haynes, 2014) p. 132
 Piers Connor, The London Underground Electric Train (Crowood, 2015) p. 122
 Ben Muldoon, London Underground Rolling Stock Guide (Ian Allan, 2014) p. 26