Put the clutch centre back on, complete with nut. Hold the clutch centre with your clutch tool made from old clutch plates and a steel bar and then try the nut. If it doesn't move then, warm it up with a blowlamp and try. These nuts are not usually too tight.
36 4G, 37 VH, 53 ex ISDT KHA (project), 54 KH(A), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.