Jeremy leaving the bodies to be found would still be a suspect. Especially with Neville having put up a fight.
Sheila would have been the main suspect. But the relatives would still not believe it & there was only one other person who had a motive to kill those five people. Other people have agreed today no one would believe a random stranger massacre or that the person who found the bodies (Barbara Wilson ?) committed the crime. Although Jeremy if under pressure may suggest the random stranger scenario.
Jeremy may have been interviewed straight away by the police & been a suspect much sooner. Especially if he showed indifference to the deaths by partying, as he did. He would have no alibi.
So it makes sense for Jeremy to phone the police & lead them in a direction on the back of Nevilles call. Giving himself an alibi at the same time which cannot be disproven. The police did not know Jeremy and would surely never believe Jeremy would commit such a horrific crime on his family. He was not known as a even a criminal, let alone a psychopath.
It also makes sense to phone Chelmsford police station, which was seven miles further away from WHF than Witham. Jeremy said he did not phone 999 because it 'did not occur to him' although dialling 999 is quicker than looking for a phone number & will result in a quicker response time.
The longer the delay between his 3.26am phone call & the discovery of the bodies, the more it gets into everyones mind sets that there really is a crazy woman with a gun still alive inside. Jeremy could spend several hours continuing to enlighten everyone about his 'nutter' sister & Nevilles phone call /alibi.
The Raid Team would automatically be called in a seige situation. Delaying things by several more hours. Jeremys Neville phone alibi is becoming more plausible by the minute. He 'should have been an actor'.
Having the police pick Jeremy up would have been even better still. It would have shown him as having just got dressed & rushing into their car. Giving the impression he had been at home all night & woken up by Nevilles call. It is also another alibi, showing Jeremy did not phone from WHF. However the police refused Jeremys request & told him to make his own way. Jeremy did the next best thing & arrived after the police. Driving very slowly.
So the phone call to the police meant Jeremy could work with & assist the police. Use his charm to become their buddies. Give them his version of events & look upset when the bodies are discovered. By 9am that morning & for the next few weeks, Neville's alibi had worked.
Jeremys supporters say 'why phone the police if you are not innocent'? Another equally good question is 'why not phone the police if guilty ' ?