It was bad policing from Taff Jones. Although I have some sympathy.
Other officers were suspicious of Bamber straight away. Taff should have been as well. Maybe he was.
But things moved quickly after the bodies were discovered and the media had been told it was murder/suicide. As the head of the investigation he quickly reached the point of no return, as it was his head on the block if the police started publically suggesting other options, with nothing to back it up early on.
Bamber had not been arrested so internally and externally Taff had to stick rigedly to the murder/suicide claim.
He couldn't publically change stance as Julie had not gone forward and the forensic evidence had not been processed. He would have looked stupid and heartless in public changing stance and blaming a man who had lost his family, with nothing to back it up. Especially if Bamber was innocent. Bamber would have no doubt made a complaint and seeked compensation from EP.
It's alright Stan Jones and co raising doubts behind the scenes. They were not in charge of the investigation.
Taff dismissed the relatives concerns, perhaps at the time correctly and through gritted teeth. However he should have had the courage to change stance prior to the relatives approaching Peter Simpson and being replaced as head officer. By that time there was enough to change stance. Peter Simpson had no hesitation agreeing the case should be examined again.
Taff should have also not been so supportive of Bamber after Julie came forward. Interviewing an in denial Bamber for 10 minutes, before announcing 'Julie must be lying'. However he was fully committed to the Bamber being guilty by the time he was arrested upon his return from St Tropez.
Sadly for Taff he never got to see how things unfolded.