[Steve in Pudsey]

That's very strange. I assumed it was a vision mixer or mosart failure followed by Studio A opting back to network (NC) when they realised they were stuck.

CCM did a router switch to put SET on air per buddying arrangements, then having had the nod from Studio A (or another NBH studio that was taking over) that they were ready to continue reverted the buddy arrangement and put the London output back to air. Why this was carrying the sustaining feed rather than SET for a smooth transition is a mystery.

However for there to now be a sound fault, only on certain platforms, seems like the whole thing is a routing issue. But I thought that all happened in the digital domain with sound and vision combined.

I wouldn't be surprised if London's opt infrastructure is different to the rest of the country however, but it's a bizarre one.