Inspector Sands and why the London Underground keeps asking for him

If you travel by train a fair bit, you are going to get used to hearing the tannoy summoning Inspector Sands, and most of us know it’s some sort of code for a problem, but what sort of problem?
Typically, on the London Underground, you might hear a pre-recorded announcement saying “Would Inspector Sands, please report to the operations room”, it’s a fire alarm in the operations room – or wherever Inspector Sands is asked to go to.
Not an order to evacuate or anythin