C Stock
In short
The C Stock was a fleet of sub-surface trains used on the Circle, District, and Hammersmith & City lines of the London Underground. These trains operated from 1970 until they were fully replaced by the S7 Stock in 2014.
In plain words
These were specific types of subway carriages designed for London's underground network. They helped move large numbers of people around the city for over forty years before newer, more modern trains took over their routes.
A simple example
A commuter travelling on the District line in the 1990s would have likely boarded a C Stock train to reach their destination.
Why it matters
They were a vital part of London's transport infrastructure for decades. Their retirement marked a major shift towards more modern, air-conditioned rolling stock on the sub-surface lines.
Easy to mix up
Do not confuse them with the current S Stock, which is the newer generation of trains used on many London Underground lines.