its what you get john,when one tries to be too clever.you can see why he spun that tale about the call'because he had to be there with police .not only to lead them down the garden path but also to show it couldnt have been me i was outside with police .also pretending seeing movement upstairs, to further reinforce it 
Correct Sami, we can read Bamber like a book. His plan was so simple that even some of the police like Taff Jones were taken in by it. Unfortunately for him however it took many more shots that he ever anticipated or planned for allowing Nevill to get downstairs and the fight over the kitchen table. That is where his attempt to blame Sheila should have ended but he made the mistake of carrying on regardless. Sheila never fought with Nevill otherwise she would have come off second best.
This case is by no means rocket science but good old fashioned detective work.