Whether Nevill Bamber sustained injuries as he hit the coal scuttle or not doesn't really change anything as far as guilt or innocence is concerned.
There was one almighty fight in the kitchen, but the order of events, and exactly what implement caused what injury will never be fully known.
If you believe Jeremy Bamber killed his family, as I do, then something very telling was when Brett Collins (his friend) asked him if he killed his family, and Jeremy Bambers answer was 'You will not believe what happened'
I use sentences that begin 'You will not believe...' quite a lot to explain to someone the monumental struggle I had, just to achieve a simple task, when that task was unexpectedly difficult.
I've also heard that sentence used many times by other people in the same circumstances. That sentence is like an autopilot thing where you're not even aware that you are using it.
June Bamber and Nevill Bamber were never meant to get out of their beds, and that sentence 'you will not believe...' is an indication to me of the monumental struggle Bamber had in executing his family, and I believe it referred to the shock of seeing his parents both getting up out of bed after being shot, and the fight in the kitchen. Murdering his family was supposed to be a simple task, but it went catastrophically wrong.