A question for those in the know, please.
The Ten Tunnel (Zig Zag) Deviation was opened in 1910. Initially it was steam operated. In 1956-60 Electrification was installed.
Did the electrification cause the rail level in the tunnels to be altered (lowered)?
In 1970 the V Sets were introduced. Was the rail level altered to provide clearance for these double deck carriages? I know some of the soffit bricks were removed to provide clearance at the roofline.
Some time after this the tunnel floors were excavated and replaced with concrete slabs. Was the rail level altered when the slabs were constructed?
I would greatly appreciate advice pertaining to these issues.