jjb1970 and Andy Y - you've both summed up APT-E!!! It is the railway's Concorde, Blue Bird, Saturn V rocket and it comes from that time glorious time when we were experimenting with the "white heat of technology" when man believed he could make super-sonic commercial air travel a reality, go to the moon, or develop the micro-processor...
However to me the APT concept is like another great British 60s idea that was never allowed to reach it's potential and sits in a museum: the TSR-2 fighter plane
Just my thoughts