I think the film showed him escaping from a B707. At that point I totally lost interest in this piece of fiction! Totally impossible. But, the rear toilets of the VC10 had a secret release catch that would allow you to climb into the rear tailcone between the engines and back to the pressure hull. I cannot recall whether there was a hatch to the ground- I imagine there probably was. But it would take knowledge to know you could actually go out through the toilet wall, because the whole thing would swing in. I actually found it on the Brooklands one and it does still work!
But I'm sure his whole story is garbage. There are no alleged 'victims' who have ever come forward, and I believe official records of his convictions appear not to actually exist. I think it likely it is all self promotion to sell his book.