Doncaster was just short haul, so it’s a bit different.  New York is not a great example either because you can get there from Bristol. However companies with headquarters in Tokyo, Shanghai, Sydney or Rio are never going to setup their UK office in, say, Wales or Cornwall if they need to travel via Heathrow or Gatwick. However given setup and operational costs, they may well do of there was a more feasible airport. That becomes like a snowball rolling down a hill…

Remember when they built a new lane on the M25 and said that it would solve the congestion? All it did in the end was result in 5 lanes of stationary traffic instead of 4.