"Mizter T" wrote...
... then Euston is regarded as
the obvious choice of the London end of it as it has enough space to
accommodate it.

Whuh?

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

Indeed, all my reading suggests there's zero likelihood.

HS2 will be tacked onto HS1, allowing for Eurostar to (eventually) fulfill
my Dad's ambition of traveling from Edinburgh to Amsterdam without changing
trains (My grandchildren might just make it!).

But in practical terms, that means New Build starting from a junction on the
Stratford-StP link, heading off to Heathrow and Watford Gap.

As many of the trains *will* go HS1HS2 without terminating, the terminating
facilities at St.P can shared between HS1 & HS2 trains that do need it.

Effectively, HS1-HS2 will be a continuous line from the North (or at least
the W Midlands) to Europe, with a spur for St P, accessed from both the
North and South. Some trains will go into StP and reverse out, most will use
the Stratford/Ebbsfleet/Heathrow interchanges.

If Eurostar (or its successor) gives in to the pressure to terminate all in
central London, then you can bet that an open access operator will choose
not to, and cream off all the through traffic.

Such a scheme does several things:

1. It saves the cost of 'new' International Terminus half a mile form the
current International Terminus
2. It saves passenger confusion and movement
3. It takes advantage of StP's interchange facilities (MUCH better than
Euston's)
4. It (finally) provides a raison d'etre for Stratford-I
5. Euston does NOT have 'space' to spare to give away 4-5 segregated
platforms for a 'new' service
6. The central London requirement is the junction for N-bound HS1 trains to
bypass St.P, and the spur for Europe-bound HS2 trains to access StP. Much of
that already exists!

The days of jigsaw railways have gone; to compete effectively with domestic
airlines, a little join-up thinking will be required by DfT
--

Andrew

"If A is success in life, then A = x + y + z.
Work is x; y is play; and z is keeping your mouth shut." ~ Albert Einstein