The article on the Bamber website is unclear, as it states both the cordless telephone and the blue telephone were not working, yet later states the blue telephone was in working order when police arrived. https://www.jeremy-bamber.co.uk/telephones
Going by the long gap between phoning Julie & the police, his attitude towards his options with the landlines were -
Calls can't be tracked. But I will phone my AM anyway.
Calls can't be tracked. So I will not make a call from WHF.
Don't know if calls can be tracked. So will answer my own call.
---------
If the 'last number dialled' phone was available, he would have phoned his AM. Then cycled back at 100% if this phone displayed 'time of call'.
Or used this phone to answer his own call.