Nevill will not take Julie seriously.
Agree he could catch Bamber in the act that night if he waited up
Not take her seriously?
Long term plans, kitchen window, June's bike, doing CC a favour, 'tonights the night'.
This together with Nevill's relationship with Bamber will have him taking it seriously.
Phoning Bamber will not tell Nevill anything. Bamber will deny everything. Waiting up & seeing him arrive at WHF will show Bamber is wanting to kill him.
Nevill may show Bamber mercy and not call the police. Bamber would deny everything anyway. Disowning him is punishment enough.