It is one of the split rings John but the valve didnt drop. It opened up the valve clearance so much that it wrecked both the opening and closing rockers, the cam shaft, the valve return spring and the shims.
Nelly being the absolute star that he is managed to sort it for me.
Funny thing was the bike was running fine apart from a tappety noise. Of course by the time the noise was loud enough to hear all the damage had been done.