"What we can conclude therefore, is that the rooms beyond that internal kitchen door was off limits to Neville Bambers killer, who could not go beyond Neville's body sat in that chair behind the door, thus preventing the killer from taking the sound moderator from the guns barrel and concealing it inside a cupboard in the den.
...
So, with Sheila being killed off last of all, upstairs on the bedroom floor with the sound moderator still on the barrel of the gun, her killer would have to remove the moderator, go into the upstairs bathroom, unbolt the wall panel that afforded access to the other upstairs part of the farmhouse, and go all the way down the back stairs, into the hallway outside the internal kitchen door behind which Neville Bambers body was sat and blocking the door off, turn into the den, go to the cupboard in the corner of the den, rummage about until the killer found an almost empty ammunition box and place the sound moderator inside it, replace the box, shut the cupboard door, and then what?
Well, presumably the killer would then have to back track his way out of the den, along the back passage, up the back stairs, go from one side of the upper part of the farmhouse on one side of the bathroom panel, to the other, making sure that the killer remembered to bolt the bath panel, and then what?"
Mike 2018