"Andrew Heenan" wrote

The assumption that Euston will host HS2 is way off; I don't think
*anybody*
regards it as the obvious choice.

Most of the trains and passengers using HS2 will be travelling to/from
London - the trains will in effect be diverted to HS2 from the WCML (leaving
space on the WCML for commuters and freight). Diversion of these trains to
HS2 will vacate space at Euston, which can be used for the HS2 terminus. St
Pancras could not accommodate an extra 12-15 InterCity trains each hour.

Most of the trains on HS2 will not be running through from HS1 - the few
that may will be able to use the Camden Road - Primrose Hill link. Not
ideal, but can a business case be made for a high speed link between HS1 in
the St Pancras throat and HS2?

Even if any Central London station could be set up for North of England -
European Mainland trains to call (allowing for any necessary security and
border formalities) it is likely that in practice most trains would continue
to terminate in London.

Peter