UTV Fault

Yes, that makes sense, I suppose.

We are back.

No 'ITV' transmitter employs RBR/RBS back up AFAIK ?

Some C4 transmitters do, but only if the RBS source is from the same 'Macro' region. For instance C4's Hannington RBS source is Mendip, rather than CP as used for the Beeb.

What about in the event of failure at Crystal Palace? Croydon takes over broadcasting ITV and C4 with a rebroadcast of Rowridge doesn't it?

I've seen them testing it overnight sometimes, the screen goes fuzzy for a moment then comes back with ITV SOUTH Teletext from Rowridge, even though the signal's coming from Croydon.

The Teletext is indeed sourced from Hannington (from Rowridge), but the video and audio is AIUI still fed from South Bank and HFR via landline. The reason being that the ITV/C4 Teletext servers are situated at each regional primary transmitter, in London's case at CP, so obviously a power failure at CP takes them out too.

Which begs the question - if the line from the South Bank to CP went down but the line from the South Bank to Croydon was serviceable, would Croydon take over or would CP go into RBR Hannington mode?

Good question, dunno.

There's no technical reason why not the latter. It just depends whether ITV Ltd and C4 decide to sustain a service from the 'wrong' region that would still mostly have the 'right' programmes, or they take the view the commercials would be wrong, and so not bother. I suspect the latter.

BTW to correct what I said yesterday. ITV do have RBS systems, but only within a region. For example <Hannington RBS Rowridge>, I've seen that one cut in when the line from Meridian Newbury failed.