[Neil Jones]

Interesting. Who defines this? Is there a government department that sets the official times for lunchtime?

There was the Ministry of Lunchtimes, part of the Department for Mealtimes, but it was abolished by Theresa May in 2017.

Indeed, there used to be a bunch of Ministries, before various PM's abolished them all.

Department for Mealtimes was a consolidation of the previous breakfast, lunch, dinner and supper wings of that department in 1992 - breakfast insisted on stopping at 9:25am for some reason, and never happened before 6am.

The other Ministries used to be located in Euston Road in London, Broad Street in Birmingham and somewhere in Southampton, which was relocated to Maidstone. There are probably other examples.