When someone comes unstuck or gone off the rails. Or a situation doesn't quite go to plan.
"Dave's in hospital, he's gone Pendolino after seeing his wife with the milkman" or "this cunning plan of yours has gone a bit Pendolino"
adjective Broken. Useless. Worthless.
Sorry I'm late, my train was pendolino.
What a pendolino idea, you moron!