Basically, the police blabbed enough on various occasions after the trial for his supporters to know exactly what happened.
Sorry if this appears rude to Aunty, but that is a very silly thing to say. The police did not blab to anyone outside of the the immediate police circle and that ensured that nobody else knew what was divulged.
Certainly, ACC Simpson mentioned in a press conference that a silencer was found on 7 August and it was reported in the local press, but the Essex Police tape recording of the press conference is 'missing' the section where he discussed it and EP now deny that he said anything about the silencer.
The Stokenchurch enquiry was not made available to the CT until 2011 and Stan Jones would never have expected the public to know anything about what he discussed with the Met. Likewise with the high definition digital crime scene photographs, none of the police would have anticipated those becoming available to the CT.
Milbank has revealed some information nearly 40 years after the event, his excuse for remaining silent is that nobody asked him previously (which is not true).
So how does the CT get access to information that has either been deleted, withheld or kept secret?