This is a minor change but I thought it was best to document it.
The factory typically shutdowns at 16:00 but for some reason I thought it was 18:00. Because of this, 'factory1' (the light-meter used for testing) was not shutting down properly. The factory's power was cut at the end of the day (again typically 16:00 but not always) and the Pi would have a dirty power-down. This, also, meant the server and its opposite relay [return-to-ritherdon/relay] would think it was still on but sending no new readings.
All of the above has no great effect of the **note** left in the README but I thought I should change it on the off-chance someone copies that line into a part of the system.