There is new evidence, and also evidence that was witheld.
E.g. that the shopkeeper who id'd him had already seen photos of him, and received a large reward.
E.g. a break in at Heathrow airport.

Had a scond appeal been heard it is highly probable that his conviction would be declared unsafe, leading to release and compensation.
Uk and Scots govts. hugely relieved to have avoided that scenario.
Very convenient.