|The bush mechanics ...|
When the noise worsened so dramatically though, identifying the source was much easier - a very worn universal joint.
Unfortunately, there was no mechanic available to fit the part. One was off sick and the other quite stressed/cranky by the backlog of work. We were able to purchase the necessary universal joint (from a mining supply shop as the mechanic was out of stock) and then Nick worked to replace it back at camp, using what tools he had. A neighbouring camper, Simon, very generously offered much-appreciated assistance and additional oomph!
(The new part went in relatively easily, it was getting the old one out that took most of the time/effort).