[JMT1985]

It wasn't until the early 1970's that the restrictions were relaxed. ITN's First Report (the precursor to the News At One) was literally the first bulletin of the day at 12.40:

tvark.org 

ITN would have loved to have had a regular lunchtime news on weekdays, but the hours were simply not there.

For anyone who doesn't know this, in the 1960s for example, ITV was limited to airing 35 hours of regular television entertainment during the week and had 15 hours to cover the weekend, that is just 50 hours of television per week.

If ITV wanted to air anything else, they had to rely on "exempted programming" which was schools programmes, adult education, religious programmes, special occasions/state occasions, Welsh language programming for some bizarre reason and then rely on "outside broadcast allowance" which allowed for sporting coverage. ITV companies were also rationed here, by the mid 1960s they were only allowed 300 hours per year to cover outside broadcasts such as sporting events.

This averaged out at 7 hours per weekday and 7.5 hours per weekend day - and so the companies, after the near disaster of their launch, chose to keep to the more cost effect and advertising ready slots of around 5pm to midnight or 4.30 - 11.30pm as their core daily weekday schedule of the rationed hours, meaning no room for a 20 minute lunchtime weekday news

ITN did offer a short lunchtime news summary on a Saturday back then