Well done, with a little help from Paul, you got there, as he said you have both tickled the answer.
It was a broken loop, line conductor had broken. I found it in seconds because the dining room had a stupid decorative metal fitting, hence I knew it would be broken here and not going into the next fitting.
In the real world you use a voltage tester and work from the last known working fitting.
In college you would need to find it using dead tests.
Well done to both, the reason I left it a while was because inevitably given time you will start to doubt your ideas.