"E27002" wrote

The tunnel was never built. I am not arguing that it should have
been. However, provision was made in the foundations of Marylebone
station ans IIRC The Great Central Hotel for it to be built at a later
date. Again, IIRC, it was intended to allow freight trains to access
goods facilities in the City of London.

I don't think Watkin had completely abandoned the idea of through trains
from Manchester to Paris via W******d, the GCR, a spur at Marylebone, the
Inner Circle, the East London Line, the South Eastern Main Line, and the
Channel Tunnel.

Peter