Of course if the phone call never happened ,there are no words to have a play on.
https://murderpedia.org/male.B/images/bamber_jeremy/20011745.pdf Page 25.
vii) The appellant’s account of the telephone call from his father could be proved to be
false for the following reasons:
a) His father was too badly injured to have spoken to anybody;
b) The telephone in the kitchen was not obviously blood stained;
c) As a matter of common sense, Nevill Bamber would have called the police
before the appellant;
d) Had the appellant really received such a call, he would have immediately
made a 999 call, alerted the farmworkers who lived close to the farmhouse
and then driven at speed to his parents home; and
e) Instead he had spoken to Julie Mugford before calling the police. When he
subsequently contacted the Police, it was not by way of the emergency
system."
The girls at the flat seemed to recall the call by Jeremy was nearer 3:00 AM rather than 3:30. Jeremy called the Police at 3:30 so it wasn't that much delay as they make out.
It is an odd situation to be in, to be requested to come to a house where someone has gone crazy with a gun. Jeremy could have felt he was being set-up and someone was planning to shoot him as well. I too would let the police lead the break in to the farm house.
In the next section:
"vii) In respect of the telephone call from his father, the appellant had not initially
appreciated the seriousness of the situation and then had become frightened to go to
the farm alone."
I think that is highly likely.