OK, as we seem to be deviating: my boss, sqn ldr ops recounted a tale of when he commanded Spitfire sqn in Transport Command. Anyway he found an order in the Flying Order Book stating that on any day when no other mission was tasked they were to fly a strike down the Loire Valley.
This they did.
This was after the war and might even have been early 50s and the French objected. From that he learnt about checking the FOB against the Master copy.