Hydraulics have been put on hold for now. I found that when ploughing, with the solid bar and fulcrum arrangement, I could lift the plough form out of the ground with no problem.
What I did find today, was the left side rear hub had moved in again. On investigation, I found the dimple in the axle, was a little off centre with the extra bolt I'd fitted. The bolt was not engaging fully with the dimple. I carefully drilled down the bolt hole and opened out the dimple. I then found a long grub screw, with pointed end which located nicely in the dimple. A lock nut is also added to that. Hopefully no more trouble with that hub.
The standard bolt is still fitted above the key.