Back in the 80's the police constabularies across England did not communicate with each other.
For the Shirley Banks case, the Met sent 2 detectives to Bristol to question Cannan, but they were effectively stonewalled, because the senior officers dealing with the SB case disliked the idea of the Met police coming onto their patch.
The same issue applied with the Yorkshire Ripper, and the belief by senior officers at West Yorkshire police not wanting to accept that the Ripper may have killed further afield from their patch.
As technology has developed over the decades, the police have had no choice but to communicate more effectively and efficiently, because the various databases available to them demand it.
But back in the 80's the police really had no desire to communicate with each other, and virtually everyone outside of Greater London disliked the Met police.
The bureaucracy and red tape has always plagued policing over the years, which is unfortunate for murder victims who are abducted and deposited in a different county.