The engine would cut out unpredictably on the road at slow to high speeds. Very dangerous in heavy traffic.
I found that it could be restarted by first turning the ignition key off & then on using the starter or if I was quick leaving the car in gear with the clutch still engaged.
No cut out at idling revs.
Fortunately the local Morgan Service Agent, Cremorne Prestige Motors, found the problem to be a faulty inertia switch which was being activated by engine vibrations
They also relocated the switch away from the the oil tank on a vibration free pad.

Problem solved! What Next.