It ought not to be about getting from Birmingham to London but from (say) Glasgow to London or Birmingham to Brussels.
I don't understand that argument. You seem to be claiming that we shouldn't build a railway line between Birmingham and London because some people want to go from Glasgow to London. If we follow that to its logical conclusion, we wouldn't build any railways.
However, the inability of the United Kingdom to plan its infrastructure in anything other than a reactive and incremental way is scarcely credible. HS2 is 30 years behind the times, should start in (say) Inverness and physically connect with HS1.
Sorry, but that is pure fantasy. Given the costs involved, we have to build incrementally.
When the Channel Tunnel was constructed it was envisaged that services could run from Scotland and Manchester to Paris and Brussels and a number of "North of London" trains built (which would fit the smaller UK loading gauge).
The original Eurostar trains must also fit because they were designed to run on the existing Southern railway lines.
Their international use was killed off by the Immigration Service who refused to countenance domestic and international travellers using the same train.
Bloody Immigration Service.
The train sets were eventually used on the ECML.
[/quote]