"bob" wrote

[2] I can't remember off the top of my head when the Norther City line
opened, but it may also have been around pre-Yerkes.

Great Northern & City incorporated 1892, construction started 1898, opened
1904 (i.e after Yerkes had taken control of Underground Electric Railways.
The GN&C was independent, though with links to the Great Northern, until it
was taken over by the Metropolitan in 1913. It was operated with main line
sized trains until 1939, after which it became an isolated part of the
Northern Line, until it was transferred to BR for the Great Northern
Electrics in 1976. As part of the Northern Line, the line from Drayton Park
via Finsbury Park and Highgate to East Finchley was used for stock exchange
(dragged) until it was taken out of use, after which stock exchange took
place via Kings Cross and the Widened Lines, crossing to the Circle Line at
Farringdon.

Peter