I find this comment from the report interesting from a "human factors" point of view :
ATCO(1) reported that his usual method of working was to put the electronic strips of conflicting traffic together and suitably highlighted. On this occasion ATCO(1) had not done this.
No explanation given as to why not. I'll bet my pension that if they'd been paper strips, he would have immediately put the strip holders together & cocked them out as a reminder......