[DTV]

But the point is that if I want to listen to the radio, I'll go and do that.

But that isn't true of a lot of viewers. A sizeable proportion of the people who have watched visualised Nicky Campbell will be people who wouldn't have tuned into it on 5 Live. Regardless of the presentational merits of it, visualised radio typically expands audiences rather than splits them.

Was “Victoria Derbyshire” a cut? A specially made separate programme with high(ish) profile host, specially made “films” etc. Compared with just a standard hour of rolling news

Yes and no. It was obviously extra investment in the slot, but I believe it might have been a BBC Two idea first which then got quickly rolled onto the News channel as they saw it as a way to trim costs (although, always worth stressing that the NC consistently saw below average cuts). VD did get better at covering developing news later, particularly once reduced to an hour, but it was ultimately a retilting of the whole morning schedule towards more appointment-to-view programmes because, while it might be true that is when most UK news develops, it was never a high-performing slot for the channel.