Electronic failure but battery is ok.

[mightyWBA]

I have a Mercedes C240 which has lost all electronic power(no lights, central locking,hazards etc)
Have had the battery tested and thats fine.
Is there one fuse that could have blown which cuts all power from the battery?
I can't even turn the infa red key in the ignition.
I had no trouble with it at all,did the school run came back and went to go out again 30 minutes later and it was dead :-(

[cazzz1975]

yes, main fuse under the dash, switch everything off then check it