Basil Jet wrote:

"Another Station, Another Mile" says at...

https://youtu.be/yEiVXoalUQ0?t=580

... that the abandoned national rail lines from Moorgate to Farringdon
might see re-use as part of a plan to increase capacity on the C/M/H
lines. Does anyone know what he means?

They're being converted into sidings to stable eight S7 trains, needed
because the number of such sidings was reduced when these trains replaced
the shorter C stock. They won't be used as running lines.