Bork's recent truck plurk reminded me of a charter flight I once did. Big rush. City of Manchester to City of Inverness in the UK. A tanker truck had overturned. The big boss of the tanker firm and the chief engineer man went to inspect the truck.
They said the trailer had 3 tanks in it. If they leaked a bit it was bad.

But, if the contents of the middle tank mixed with the contents of the 3rd tank - Inverness would not be there anymore.