Series 3 Brake replacement - next step?

The locking ring stops the trailing shoe from rotating inside the drum under severe braking.

I have got a hard copy here which I can scan easy enough, but is it possible to upload PDF's to the forum?

Smithies landrover has a manual that looks like fairey hubs to me.
https://drive.google.com/file/d/0B5kIlEiLq7M8M21KMUhFVWswX1k/view
If that link does not show it do a web search for smithies landrover a NZwebsite of interest will come up.Low down on the page a link to free wheel hubs.

There is a threaded hole in the drum, and if you still have the little screws which hold the drum in place, remove them, screw one into the threaded hole, and it will force the drum off. You still need to get at the opposite side and help it off with a long lever. When you put the drum back on, make sure the threaded hole is in the right alignment, for next time.

And via the magic of the internets...