Thanks for your comments and excellent pics. Took the wheel off today and in bright sunshine could see 3 to 4mm scratch marks on the double spline. Also tried pushing the boss one spline adrift and ,yes, it jams on very nicely requiring a goodly tug to remove it.
I have also looked more closely at how the unlocking ring sits when in place and I will feel more confident now. I did notice how slack the boss is in the shaft, quite a good side to side movement. Perhaps the splined shaft and the boss are made by two different firms. The boss is made in France according to Mr Google. I have emailed MMC expressing my concerns. I have noticed, having joined the Morgan fraternity, that mutual help amongst the owners is essential given the number of foibles exhibited by the five speeders.
