Business calls were not differentiated per se...
precisely the same billing system is used across the nation, then and now (within any given carrier), then depending on the subscriber, appropriate tariffs applied... AFTER the fact.
The logs exist for private and business, esp in those days...
One telegraph pole, one wire to the house.
It's not impossible that in those days those on a business tariff might get more detailed billing, or the logs kept for longer, but with JB one would assume, connected to the same exchange as Nevill, same carrier (BT) if they couldn't get confirmation of calls JB made, then they wouldn't for NB either.
It was not too long ago that newspapers espoused the 'secret log that proves Nevill phoned the police' - which we've all seen and it hardly proves anything. Some see it as additional evidence to support Bamber, most see it as further confirmation of what we already knew... and appertains to the JB call only.
I eagerly await this new material.
