Lucas Girling Umbrella handbrake outer cable end stop, this part fits ijn the end of the handbrake lever bracket & helps hold the bracket to the bulkhead, it also acts as outer cable endstop - fits where the arrow is on the 1st photo.

This part is often broken when its removed, this is because its overtightened. 

This part & the complete Umbrella handbrake Girling Part No. GB21876 were sold under the Lucas Girling banner but made by Wilton & Co in Birmingham, as such were fitted to many British & a few European Classic cars including Alfa Romeo.