i thought that as well.
This is part of DCI Ainsley's report to the Director of Public Prosecutions on 23 September 1985:
“In the kitchen, situated on top of a work surface beneath the hatchway leading to the bottle room, was a normal dial telephone, colour white. This was in working order. The handset was found removed from the cradle.
In the company office on the first floor was a blue coloured telephone with a digital display and memory. There is no evidence to suggest this telephone was used on the night in question but it was used by an officer of the Essex Police Tactical Firearms Group after the farmhouse was entered.[9]This telephone will retrieve on the display only the last number dialled which is automatically erased by the next use. Found in the office was a third telephone on a shelf. It is believed that this telephone was from the main bedroom, having been unplugged and the cord wrapped around the set. This cannot be explained but the set and bedroom plug have been checked by telecommunications employees and both are in working order.[10]”