Interview with Chris Mullin in February:
http://www.theguardian.com/commentisfree/2016/feb/10/birmingham-bombings-police-ira
// Indeed there is reason to believe that the police were rather better informed about what happened than they have ever admitted. At least one of the IRA men in custody talked. In the autumn of 1987 someone with access to the Special Branch archive provided the Granada television programme World in Action with a five-page precis of interviews with an IRA man arrested after the bombings who purported to name one of the bombers. So far as I can see, no action was taken.
...
Two of the bombers are dead and, unless the remaining two were to come forward and confess, there is no prospect of their being brought to justice. //