What did RAF Engine Fitters 2e do during World War 2?

I would say that were responsible for the mechanical aspects of Aircraft maintenance including the test running of engines (on the ground), lubrication and coolant issues, My uncle was a fitter 2E an he told me that a 2E was the only person (other than the pilot) permitted to run up the engine/s and Taxi the Aircraft. Other ground crew members were to see to armament, and others to airframe .not sure about radio