The Mystery of Stokenchurch, Episode 3
You are referring, my dear Watson, to the strange case of the Mast that was not lit up in the night. There have been two previous threads on this and much ribaldry on the subject. It's been NOTAMed and there is a chart amendment on the website.
[Edit unedited owing to sense of direction faff induced by upside downy Chipmunking]