I have come to the conclusion it is probably ok to run with just the inner snap ring holding the shaft into the gearbox.
When I had my first maestro I had an issue with the drive shaft staying in the hub assembly when on full steering lock. As the rear hub on the F doesn't steer I think the risk is of the shaft coming out of the hub is virtually nil so I am going to leave it out. If you don't hear any more assume the shaft stayed together.
Home to black Alfa Romeo 159 3.2 V6 Q4 ,green MGF VVC andred MG Maestro T16.