If the answer phone was off QC the phone would ring but no call would be registered? I did read somewhere that the police removed a answerphone but don't quote me.
I've just realised that the answerphone theory doesn't stand up. Before I explain why, I will address your comment. You're overlooking that if Jeremy is guilty, he has obtained a second answerphone and rigged that up and switched it on prior to leaving for White House Farm. On the other hand, if Jeremy is innocent, the answer function on the phone has simply been switched off, meaning that the phone would ring on in the normal manner without the interruption of an automated message.
Now I will explain why the answerphone theory doesn't hold together. The reason is that in order for it to work, Jeremy would need to obtain a second phone that would be used that night then hid from the police, but as I have already explained, Jeremy could not have planned to stage a call as he had no way of knowing that Nevill would be in the kitchen and there was no phone in the bedroom, so he had no means to explain how Nevill could reach a phone.
A pro-guilt person could reply to this by saying that Jeremy could have planned to stage a pre-incident call from Nevill as part of an alibi, but if you think about this within the parameters of a prosecution scenario, that can't work and this would be intuitive and obvious to Jeremy, if he were guilty. The bottom line is, he has to kill Nevill in bed or wherever Nevill is sleeping. Anything else represents the plan going awry.
I am swinging back and forth on this case, but I am very doubtful that Jeremy could have carried out this plan. If he did, then I'm still struggling to see how he did it.