What an effing place!!! Has it been snapped or reduced at some point?
I agree a socket and then replace with an Allen bolt for future ease.
That's the "look at what you could have won" illustration... Plenty of plus gas on that bastªrd, if it snaps In there, it's drilling time!!!No idea but it’s definitely square, and in the rave manual they only picture the easy side!
Just a thought as I don't remember the sizes, is it possible to use a 1/4" socket extension bar on it so you have a square hole going onto the square of the plug? and then use a spanner on the end of that to turn it?