No keys = no engines = no power. Rather hard to clean in the dark. Here cleaners generally know enough to start a train.
It's generally not quite that easy, one must gain traction interlock to obtain brake release, which means all doors must be closed, DRA set to off, and any other signal/onboard systems started (on the Cambrian the driver must log into the ERTMS system otherwise he will be stopped after 7 meters).
On the class 37s, you've got to deisolate batteries, prime the engine, the fire it up before obtaining traction interlock.
