MartinM wrote:
How about South Hampstead where the Chiltern line appears briefly over
the portals of the tunnels? would be a lot of stairs!

Above the LNWR tracks that Virgin and Silverlink utilize, beyond the
tunnel mouths is the Metropolitan Line. Some distance below the LNWR
tracks is Swiss Cottage Station. In a world were passenger convenience
mattered South Hampstead and Swiss Cottage stations might become an
interchange.

Adrian.