After the (kind of) successful fix on the Torque using graphite impregnated cloth, and some guiding comments I was inspired to try a more suitable solution.
Rather than using a material with a built-in lubricant, I chose to use a slice of a thin plastic chopping board as a ‘washer’ between the two aluminium surfaces.
I don’t have a photo of it in place, but this is the remaining piece of the chopping board I used. As you can see – very thin. It has been working out perfectly – the tools angle easily, but without any tendency to slip.
The shadow (fwiw) is the top of Jessica’s trampoline – some reason I didn’t notice it when taking the photo!