Good comments Jane J.....
I don't believe for one moment that Neville rang Chelmsford police... JB did! NB was shot in the jaw upstairs, which made speech impossible, he then made it downstairs ( which we know he did probably at gun point) looked up the number for Chelmsford police although he had emergency numbers on the dial of his phone... also rang JB... and didn't leave an excessive amount of blood on the phone in the process..... Never!
Lookout, the police were under the impression it was 5 murders and a suicide when they entered WHF, to say they destroyed evidence that could have proved JB's innocence is not the case. If anything, any evidence that was destroyed was because JB had spun a good line implicating his sister! Taff Jones was in charge in the beginning and believed JB...so he would have been the one to give the go ahead to burn evidence, discard tapes and clear up the crime scene....only to find out later he was wrong to do so! Hence his continued stance that Sheila had committed suicide.... Once the police etc looked into the crime more, it became obvious Sheila had not shot herself twice in the neck.....Taff Jones was then replaced because crucial evidence had been lost! Conclusion....JB spun such a great line regarding his sister, that he shot himself in the foot regarding convincing Taff Jones of his supposed innocence.