Three companies that were separate, connected, decimated, separated and finally re-connected.

Some links to the BBC film archive (requires registration):

Construction of the new Central line, 1975: https://bbcrewind.co.uk/asset/5bd8297...

Construction of Central and 'Botanic Avenue' stations, August 1975: https://bbcrewind.co.uk/asset/5bd8297...

Opening of the new York Road station, December 1975:
https://bbcrewind.co.uk/asset/5bd829d...