BLACK ROD (n.f.) The usher belonging to the order of the garter, unsurprisingly so-called from the black rod he carries in his hand.
Dr. Johnson’s London Dictionary for publick consumption in the twenty-first century avail yourself on Twitter @JohnsonsLondon
CabbieBlog 
When I worked for the police, my department covered the armed protection of parliament. He used to be known to us as ‘Black Knob’. 🙂
Best wishes, Pete.
LikeLike
I wonder if he knew that!
LikeLiked by 1 person
I doubt it, otherwise he might have filed a complaint. 🙂
LikeLike