Merc W124 master/ECU fuse?

[crofty1984]

Hi All,
Does anyone know if there's a "master" or ECU fuse on a mercedes W124? It's a later model if that matters.
I have a project that needs a 12V relay-based kill switch I can wire into a fuse (so not the motorsport "handle" type).
I can't find anything that looks like it would do. There's a fuel pump relay, but I really could do with something on the electrical side to kill the engine dead.