W211 Interior Mirror refitting

[Paddcomp]

This mornings mishap is to knock the rear view mirror off my W211 E Class facelift 2007 (Avantgarde), which is hanging down on the wires.
There's a triangular aluminium plate which it seems to mount on but I can't easily find how to reattached it?

Any help or direction appreciated.

 

[pmcgsmurf]

It's spring loaded into the mount, needs located then a very firm push at either side to lock it back in.