Since the photo was identified I've been following up with some more research and, as this is no longer a mystery photo, I've posted it as a new subject. This accident appears not to have been the subject of a Board of Trade Railway Inspector's Inquiry and Report, for reasons that remain unclear at present. There was an 'H.M. Inspector', a Mr Lauder, at part of the inquest into the death of one of the footplate crew but he was a Tyneside-based Factory Inspector, not a member of the Railway Inspectorate.
Attached to this and the following post are eight more photos of the accident that have turned up. Three are from the Ken Hoole Archive, and they show the scene after the N&C line had been cleared of debris (including the industrial locomotive with which 2115 had collided – it had been pushed through the partly-demolished stone wall on the left) but before the derailed locomotive and its train had been recovered. There are also five photos from a private collection which advertises on Ebay.
Looking back though the discussion there are some brilliant minds at work on this forum. One of Bryan's knowledgeable crane experts said
Looking at the second photo now it's clear that's just what happened, as the loco has fallen into a coal drop following the collision.'The loco seems to have fallen into some kind of hole, or run onto a structure of inadequate strength…'.
I am posting low res versions with permission; good quality prints of all the pictures can be obtained from the sources quoted.