Used Harry Craddock’s recipe as I didn’t have any Grenadine either. A fine cocktail although I’d watch how many to enjoy before motoring out with the RAC:).
You definitely need to like Campari for this one. There are lots of different lime varieties; a friend has a tree really nice smooth tasting limes. Bumped up the crème de cassis. 2:1:1. Tastes great to me.