[QUOTE=davidjohnson6;11391436All of this will strongly discourage over 70s from south London from using the DART[/QUOTE]
No need to use the DART.
About 15 months ago my flight from Luton was cancelled because of snow and I couldn't get back oop northish because of snow. I got the National Express coach from the terminal to Marble Arch and returned a few days later using the same coach - all free using the concessionary pass.
So some over 70s from S London may use it if it still works with National Express, at least it parks almost outside the front door of the terminal.