Wow, this is a very nice Negroni variation. The coffee liquer isn't too subtle IMO, just right.
Don't skimp on the orange peel, it really really takes this one to another level.

I prefer this as an equal parts cocktail omitting the sweet vermouth:
1 oz London dry gin
1 oz Campari
1 oz coffee liqueur (Mr. Black for me)

I like the version of the bar Le Lion. They switched the Dry Gin for Old Simon Genever, the vermouth for Noilly Prat Rouge an 1,5 cl, same amount of Bebo.

Made this with. 1 1/2 cl coffee liqueur due to a comment about it being too subtle. It wasn't subtle at all! (I used Galliano ristretto). The coffee arrives on the palate late and prominently along with the bitterness. I think Diffords measuments would strike the best balance. Nice drink, although a bit sweet and doesn't beat a regular negroni.

Very nice, although coffee is quite subtle even at double the measure