[LondonViewer]

One unknown is whether the BBC would still have moved their News to Ten, and still overtaken them in the ratings.

I can not imagine a time now where all the channels put their biggest stuff on at 9pm but BBC One persisted with putting all their big stuff on at 9:30pm. It was a completely different era.

Surely that would have been very difficult, politically, for the BBC to do.
In the ‘and finally’ book there’s a mention that there was an earlier attempt to move the NaT back, but ITN managed to scare off the regional companies by warning the BBC would take the slot and compete at 9pm.
Such a huge mistake to invite such competition in your most important slot.