In the law abiding world, the worst that can happen when your diary gets found is to be bullied by your sister for a six year long "crush" on Julie Banner.
A sideways step into the criminal underworld, however, and your diary can be your worst enemy. Particularly if you're not the smartest crook in the crew.
Step forward getaway driver Jonathan Ochola who was convicted of armed robbery because of an entry in his diary (see it above).
The 21-year-old claimed he was at home watching football on TV while his partner in crime Rashad Delawala stole £500 from a Ladbrokes betting shop in Southsea, Hampshire.
In fact Ochola had the engine running and was ready to whisk his criminal colleague away. He remembered to be there thanks to his brilliant diary entry: "Go to Portsmouth, robbery happens"
(Main image: Solent news)