Peter K..those 'innocents' you refer to may not have been innocent at all....there were around four groups of people who subject to appeals were released as evidence against them was unsafe....unsafe evidence does not mean they were innocent. I would sure love to know how many of those released in the nineties and early 2000s have been in trouble since.
One of the sad parts of our UK justice system is that we can know for certain that someone is guilty but the 'weight of evidence' has to be 'enough to convict' them. Consequently many obviously guilty people have had to be released.