There is no uniform generally accepted response to every event that can occur. Everybody reacts and responds differently and it is a sweeping assumption to claim that any response other than dialling 999 is not rational.
The only rational response of someone who actually received the call Jeremy claimed- which he claimed his father sounded terrified- would be to go there or to call 999. Calling Julie to wake her up is not what any rational person would do (that is why Jeremy lied claiming he called Julie after calling police).
No rational person would then further waste time by looking up a phone station number in the phone book.
No person who did so then got no answer at the station because of the house would decide to get the phone book again to look up more numbers instead of calling 999.
His actions on'y make sense if he didn't receive the call he claimed and was just pretending he got a call. That is what Julie said he was doing and that is what the evidence proves he was doing because evidence further proves Sheila never loaded the gun, beat anyone with the gun or shot anyone with the gun. They were all murdered by someone else which means Nevill never would have made the call claimed.
His behavior corroborates and complements the other evidence that establishes his guilt.
