One of the biggest myths which was originally propagated by then shadow transport secretary Theresa Villiers is the completely crazy idea that building a high-speed rail line from London to Liverpool, Manchester and Leeds would be a viable alternative to the construction of a third runway at Heathrow airport. In fact, nothing could be further from the truth.
Consider these realities:
Crossrail is already going to bring about a massive improvement in direct access to Heathrow from numerous destinations in central and east London, including the Docklands.
Meanwhile, connections to Stansted, Luton and Gatwick are only slightly improved due to better linkage with the Stansted Express at Liverpool Street and with Thameslink services, which operate to both Luton airport Parkway and Gatwick, at Farringdon.
HS2 Phase 1 will have an interchange with crossrail at Old Oak Common, providing much quicker access to Heathrow from Birmingham and Manchester, assuming a direct service is added to reach terminal 5.
The second phase of HS2 will also enable more passengers from Leeds to get a fast connection to Heathrow, and a spur may also be added to run directly into the Heathrow complex, although I personally doubt this will happen at this stage, due to the huge extra cost of bringing larger trains into the Heathrow complex, and the dilution effect of having to serve so many different terminals.
Meanwhile, as I have already commented, HS2 will have very little impact on the domestic flights market -- for starters, there just aren't any flights from London to Birmingham, Liverpool or Leeds Bradford, whereas the train already has the lion's share of the market between London and Manchester.
There will be some time-saving or train journeys between London and central Scotland with Phase 2, but these are unlikely to be that significant, as the journey time to Edinburgh and Glasgow will still be around 3 1/2 hours.
The scenario quoted by the government is that HS2 could remove 6,000,000 seats per year from the UK domestic flights market, a figure that is clearly grossly optimistic.
Even if HS2 was built to run all the way through Newcastle and up to Edinburgh and Glasgow, and the journey time was brought down as low as the 2 to 2 1/2 hour mark, it has to be remembered that London airports are scattered over a wider geographical area. Even with a substantial time-saving between the city centres, people wanting to get to places such as Surrey or Brighton (Gatwick); Bedford, Luton and Milton Keynes (Luton -- remember, Milton Keynes is not on HS2); or Cambridge or Basildon (Stansted), might still be more likely to fly, if such routes still exist by then, giving the extent to which the double helping of APD already clobbers domestic flights.
Even if the 6 million figure was true, any runway built in the south-east will be done so with the aim of increasing capacity by at least 25 million passengers per year in order to recoup the investment.
Clearly, there is nothing to compare.