Good stuff again Sparky. 
BTW I've always wondered how the regional ITV companies timed their ad-breaks when they 'patched in' for network programmes and whether any of these over-ran as ad's shown by Granada, Central or Thames would have different timings and regional variations so did they get a specific time of say 4 minutes and 35 seconds to fit their advert and continuity breaks around or did the ITV company showing the 'patched in' programme delay things at all?
Thanks again. 
The during the 60s, representatives from each of the big ITV companies met weekly and discussed the schedules.
This is how many a ITC show was born, with the legendary Lew Grade selling ideas to the network, long before scripts were even commissioned.
However - the schedules were drawn up by the ITA/IBA, and each company would contribute details on their programmes.
ATV (I had a photo of this somewhere...) scheduling department in Birmingham had a wall dedicated to this, marked Mon-Sun, and the times down one side.
Each programme would have a particular colour, and these would be arranged to suit. This being pre-spreadsheet days!
With the programme information, they could work out timings of advert breaks, junctions, continuity announcements, and trailers/promotions.
It was here that the "slack" was added - to allow for the few seconds difference here and there when regions linked up.
As mentioned previously; they had a conference call system linked to all the regional control rooms - where timings and changes could be discussed.
If (say) ATV were linking to "Thames" for the 'Sweeney' - the links department would patch the link sometime before this to ensure that the picture & sound was OK; this would be indicated by colour bars, a tone and the station name overlayed.
Prior to the 'Sweeney' starting; Thames would tell the other regions that their Ad Break/Link before this would run for so long and that the Telecine/VTR would be started at a particular time. Normally a 40 second countdown.
On the monitors at the ATV end - they would see the countdown clock from the Thames end; which is also fed to the announcer studio - and they would link as required.
All looks seemless to the viewer - but in actual fact, the poor announcer is watching the clock, talking to camera, and has a floor manager and Transmission Director shouting orders too!
If they were short of time; ATV could A) drop an advert, B) Drop a trailer or C) Cut the announcers link short
If they were waiting for Thames, they would run additional trailers or get the announcer to thumb through the TV times and speak about what might be on next week.
It was the responsibility of each region to switch to the programme on time.
I'd love to see how they do this in the USA - given they have different time zones.
Incidentally - timing for all stations were monitored by clocks sychronised across the network; and they used the speaking clock.
