This is annoying me now!
I'm sure I've heard reference to the R*man connection before. You haven't asked here before, have you?
Checked out Camden Town Past which covers part of the history of Primrose Hill, but sadly only from the 18C onwards, so no luck there. I found various vague references to Boudicca's grave being placed on Promrose Hill, but nothing solid to go on so far.
Obviously, if you find anything, please put me out of my misery.