[Stooky Bill]

Regards the TV-am to No. 73 phone call, this was an explanation I got on the Southern, TVS group on Facebook.

It looks like the transmitter switch from TVam to the local ITV stations happened at the end of WACaday - you can see the recording lose servo-lock when the close-up of the phone key pad appears suggesting a non-sync cut. (The cut from TVam to the local ITV franchises was non-sync ISTR as it was done at the lines level?). I think that TVS will have booked a feed of the output of the TVam studio in Camden to allow the two-way to take place - then I suspect the No.73 gallery will have played in the TVS ident ?

Yes, the TVS ident will have been on the beginning of the title sequence. It was standard practice to edit the production company ident onto the title sequence. This of course how it is able to fly through the letterbox of the red door. 

That's how I assumed it worked, it's not quite tight enough to be recorded, and when would they have done it? Even if there was an ad break between the two programmes that's as good as doing it live (they couldn't clip up and file transfer back then). 

As for the comms between Timmy and Sandi I'm pretty sure they went by this actual phones. Looking at the clip again, the wire of Sandi/Ethel's phone goes up and over the piano. Looks awful and not something they'd do if it wasn't necessary to wire it in somewhere. In those days it was quite normal to have actual live phones on studio floors, often it was the way the presenter was communicated with. 

Phone lines are still used for TV comms, either land lines or mobile lines. Generally they're a lot easier than getting circuits set up and also will often be a lot more reliable. In this case why get a 4-wire route from Maidstone via the tower to Camden and through the galleries at both ends when there's already the telephone network available?