Crossrail 3 not crossrail 7

If Mayor Boris wants a birmingham thames estuary airport link then the line has to be designed into HS2 euston rebuild and around the tube and Crossrail 2. That will require some design stage and planning alterations to any plans developed so far. The trains in use would be London Midland services and would probably run from milton Keynes Rugby or Tring depending on desired  type of service pattern and use of current infrastructure.