[Clean Feed]

I guess it's possible that the nature of the C4 operation meant that the sync was closer to being in sync than on ITV so the switch was less visible.  For example opportunities for the regional C4 suite to genlock sync to the incoming feed.  A round trip via TV-am at the London end might add the same kind of delay as a round trip via the ITV station at the other end so the two versions end up roughly in sync.

Or, did Channel 4's playout receive Channel 4 Daily + ads via TV-am, and that TV-am source was a genlocked source on the playout desk - hence no switching? Assuming, the ads were broadcast nationally.