Hmmm, I have just seen the entry you have for William on the Backworth Maud website. I see that you have his date of death as 26th January 1946.
In theory his death should be registered in the March quarter of 1946. I can see only three plain William's registered with an age of 58, these being in Edmonton, Swansea and Tynemouth.
Tynemouth is about 30 minutes by car to Durham.
Was there anything in the newspapers about the rock fall at all?