From 1968-on, the Mini incorporated a steel sleeve into the lower A-Arm bushing. It has become quite common for this sleeve to fuse itself to the fulcrum pin, to the extent that the pin sometimes will have to be cut to be removed.
The diameter of the shaft where it goes through the bushing is exactly 1/2". If you have successfully removed the pin and it is larger, the sleeve is still on the pin.
If you look closely, you will see a seam in the sleeve running lengthwise. By using a hammer and chisel you can spread the sleeve apart, and it should then come off. If the fulcrum pin cleans up okay and still has good threads it can be re-used. If in doubt it should be replaced.