I've gone through this quite carefully and it is a very odd accident indeed. One comes away with the distinct impression that something out of the ordinary must have occurred on the downwind leg to distract the pilots from the altimeter.
On a slightly different tangent, the Wikpedia entry has quite a few errors and I wonder if it's worth the trouble correcting. The references are to a book, Barker 1988, whereas I would use the Official Enquiry Report.