BA don't need a back up plan NATS already have one devised. It's called following the taxi instructions using the taxi chart, although after a long flight it is much easier to be told on vacating "Take the first left, follow the greens" than " First left on Alpha, right at Block 12, left on Bravo hold at Juliet".
The system is the best in the world
and the options being the ICAO placarded nightmare that is MAN!!
