Prepare a rocks glass (9 ounce) into which squeeze 4 wedges of lime (drop the limes into the glass after squeezing).
Add a bar spoon of brown sugar and a measure of Campari. Put the bar spoon into the glass, flat side down and add crushed ice.
Give it a bit of a stirr and top with soda.
If its a bit too bitter you could whack in some gomme or more lime juice to taste. Its a bitter drink, sugar/lime is to take the edge off it and make it tasty :)