Took down the Lucas starter from my Cortina Mark 4 to change the armature. It was turning over very slowly, seems the old commutator had some wear in it. Installed the new armature and works nicely now. I did find that a pair of snap ring pliers would really come in handy for this job which I didn't have, had to pry the ring on the pinnon shaft off and then squeeze it back on with some difficulty (not all shown in vid because camera batteries died).
Lucas Starter, Starter, Cortina, Mark 4, Mark IV, Ford, Ford Cortina, Commutator, Starter motor