[Bluecortina]

That is true, but before 1993 the local teletext was all from Oracle, albeit I think with the actual content provided by the ITV companies.

After 1993 the ITV companies got responsibility for subtitling and the 600 magazine (the 'Ancillary Teletext Service) which could only be TV related content. That was originated at the ITV company. Channel 4 had the same but the 400 magazine, and Channel 5 with 500

Meanwhile Teletext Ltd also provided local content but it all came from them and their providers. They were more local than ITV, as their service originated at the transmitter sites and they could potentially broadcast 25 different teletext services on both ITV and Channel 4.

Pre 1993 the national teletext service was (finally) originated at ITN and this included the local teletext services for LWT (and I presume Thames). It was one of the reasons ITN was permanently fed to Thames and LWT. This ITN teletext feed was bridged across to all the Thames/LWT's main outgoing circuits which then of course fed all the other ITV companies who inserted their own local content over the London regional content.

Post 1993 London's regional teletext service was inserted at TLS. But there was no actual derivation of content there, this was provided by a third party who modemed it across as required. I think you posted a link earlier to a chap who used to work on this service and has much more detail. We didn't really need to touch it, it was all Softel kit and I do not recall it ever going wrong. I think they may be an IBA engineering information booklet on the origin of teletext distribution arrangements which started at South Bank and Thames but was eventually amalgamated at ITN.

Edited to add. Have a look here if you are interested in the history and development: Number 20 is the pertinent booklet.

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