Very very weird aspect of the case. A strong point talking prosecution wise. But when you look at the broad picture it doesn't add up.
Why would the gulity bamber tell her of what he was planning to do? How would he know that she wouldn't dob in him straight away. Wouldn't it have been better from bambers perspective. If he had been scheming this... From 1984 at the earliest.. to keep it all to himself?. He had no reason to tell Julie of what he was doing. Bamber isn't an idiot. He would know he would be digging himself an hole. She would bring the whole thing crashing down. Who could live with the fact knowing their partner had killed his family and got away with it?, Of course bamber would be aware of this. Of course he would readily knew the potential damage he had done by confiding in Julie mugford.
Look at bambers behaviour post massacre. Having it off with other woman. His closeness to Brett collins. Distancing himself from Julie. By bambers own words by early 1985 he was losing interest in julie. Its madness to think that Bamber would tell her of his murderous intention from the outset. But to carry on like he did post massacre..... He might as well have said " go to the police and tell them"
I'm not aware of Jeremy bamber ever saying on record. Or Julie mugford stating that Bamber had threatened her with the words " if you ever go to the police I will end you" he, as his behaviour suggests didn't care much for Julie. He wasn't afraid of the fact she could bring down on him. Which rationally you think he would be
It boils down to Jeremy bambers arragonce. His stupidity or it never happened