I too once believed Sheila was the culprit, for many years until I became familiarised with the facts. Without doubt it was the telephone call, that I kept coming back to. Again and again and again, looking at all the details surrounding the house of cards that is the alleged telephone call. It's clearly an invention to enable him to be first on the scene and get the police to accept his narrative of the deranged sister.
Here in the real world, Nevill would clearly simply disarm Sheila had she got hold of a gun. At a stretch you can see him dialling 999, not Jeremy and certainly not leafing through the yellow pages looking for the police telephone number
Why was the bedroom telephone moved prior to the murders? it was found hidden under some newspapers in the kitchen. Because Jeremy couldn't risk Nevill dialling 999 from his bed once his sick operation was under way.
The absurdity of penthouse model Sheila duffing up a strong farmer in a life or death struggle, battering him to death without so much as breaking a fingernail.
The scene of chaos in the kitchen, with raw sugar spilled and crockery all over the floor. Yet the soles of Sheila's feet were clean as if she had just got out of bed (Jeremy's fans explain this with bubble bath before suicide)
The fiction of Sheila loosing off shots with a semi automatic rifle in the first place, reloading and the absence of forensic evidence on her, coupled with Jeremy's lame excuse about shooting bunny's and leaving the gun out the night before.
Boy racer Jeremy being overtaken by the police on his way to WHF where according to the phone call Sheila is running amok with a gun. Here in the real world Jeremy would be rushing to the scene.
The discrepancies in time between when Jeremy called Julie telling her all is going well so far, and when Jeremy claims the call was made. The time given by Julie's housemate casts further doubt