Jabird
An uncosted link between HS1 & 2, which may handle a train or two per day from north of London into the Chunnel under current plans.
A much better option would be to re-think the Euston design - turn it to face east-west, and use the airport or Ashford as a terminus for HS2, with many more Eurostar / DB etc trains then being able to run north as they are able to set down and load again in this station.
I don't think it has to be this complicated, Jabird.
London is a major stop, so I see little reason for a through track. Just make all the TGVs stop at London.
Ok, so:
The trains come in from the Chunnel.
They stop at Silver-Boris (or most of them do), and split there.
Half the train goes north (Foster's new northern bypass), and half the train goes to London.
The London train loops into Kings Cross-St Pancras from the northeast, as usual.
Outbound, it goes north and loops west to join the current HS2 track, up to Birmingham and beyond.
Why bother with Euston at all? Its a waste of time, energy and space. We already have a perfectly serviceable London TGV terminus at KC-SP, so why not use it? Besides, KC-SP is a much better terminus to use as it is on 6 metro lines. Euston is an absolute pain in the a*se, as it is not on the circle line and nigh on impossible to get to.
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