That is one rusty rear quarter!

Started stripping the passenger’s side rear quarter panel to find out what was going on with all that rust and filler back there:

It didn’t take long before I excavated evidence of, yet another, dubious repair job. Using a drill-mounted wire brush I followed the path of destruction the former repair around the edge of the rear panel to understand how much was original metal and what was thin-gauge aftermarket stuff:

So, it appears that all the metal below the swage line and up to the wheel arch will need to go and possibly the wheel arch itself. Thankfully everything above the swage line appears solid and in good order, so this will be a case of chopping out the large aftermarket quarter panel and the other key areas where the pervasive rust has crept. On the plus side, this will give me enough access to treat the inner door metal work, which is notoriously tough to reach. These inner areas came from the factory with next to nothing in the way of rust protection, so it will be reassuring to give it some rust prevention. 

It all sounds easy when written in a concise paragraph like that! Now to source a replacement panel and fire up the reciprocation saw....