That is true Keira but I deliberately didn't include that as I've always thought it unlikely. If there was coercion then the point of it would presumably have been to get Jeremy to come to the farm so that he could also be killed - in which case would they not have made a point of getting Ralph to tell Jeremy not to phone the police?
If there was coercion:
1. Nevill could have been in so much pain, under so much pressure and so exhausted that he messed up what he'd been told to say.
2. Nevill might have attempted to deliberately sabotage the message that the person coercing him had told him to pass on.
3. Nevill may have tried to suggest on the telephone that all was not as he was telling Jeremy it was and could have been interupted by the person coercing him (and subsequently beaten?) for deviating from what he'd been told to say.
4. Nevill may have taken the opportunity to fight back during the call, catching the person coercing him unawares, so interupting the 'text' of what he had been told to say.
5. The person who was coercing Nevill could have been in a deeply disturbed or psychotic state, so may not have even considered the possibility that Jeremy might call the police.