[Steve in Pudsey]

Multiple observations on the London heads:

- At the start of the regional heads, on One HD, notice that the headline lower third is still in vision over the London presenter for 0.5 sec before animating off; while on the NC, the lower third gets dissapeared "immediately" after the opt to sport heads.

- At the opt in point of the regional heads, the London presenter holded off for a few seconds, allowing the titles be played in full; on NC, the titles is played midway.

So I'm pretty sure that the sustaining feed of Studio B now plays the London heads rather than sports heads, and runs the regional heads running order for London. It's definitely not as someone mentioned the London heads and sports heads go out from the same gallery via different engines and TX lines, else both channels would see the titles running in full.

My assumption is that at the TOTH, Studio E or C (whatever gallery that plays the TOTH countdown on the NC) takes Studio B's feed "output on the output", so to allow them cut to the sport heads at the regional opt out point. Then, at some point during the titles, they activate the network switcher and switch the NC's TX to soft-opt into Studio B fully. Perhaps some insider here can correct me on how they updated the workflow for the regional opting.

I don't think anything there proves beyond all doubt that Studio B isn't playing out both versions (you could have one event in the running order to cut the news channel away when the opt is called then another - after a brief pause to let Nations and Regions opt cleanly - playing the London opt).

However I can't fault your logic - certainly your video confirms that London is getting to air via Studio B for the headline sequence (which I think is a further argument against the idea that the London headlines come from D, were that the case surely they would have continued to have D opt out?). It would make sense for C or E to handle the NC headline fillers in the way you suggest.