[Brekkie]

I doubt it would happen with a pre-recorded show but it has certainly happened with live sport - if BBC Wales has opted out to show live rugby for example it might then opt back in to join the snooker on the network for example - and similarly viewers in the nations used to often leave some shows early too (I think Children's BBC would often say goodbye to viewers in Northern Ireland). But yes, for an unexpected event we'd usually delay or adjust the schedule rather than just join the originally planned schedule mid-programme.