Filleting a mackerel is a nice skill: ‘nice’ in the sense of requiring precision, deftness and care, but also implying a certain pleasure in the task. A sharp knife is required, and two quick cuts behind the gills start the procedure. With the fish on a board, you then need to make two long, parallel cuts either side of the backbone, only as far as the central vertebrae, on both sides. You then manoeuvre your knife around each side of the backbone in turn, proceeding to cut all the way through past the stomach cavity, thus separating each fillet entirely from the bone. Thereafter the knife should be slid under the ribcage, which must be cut away before facing the greatest challenge, the removal of the line of tiny pin bones that protrude at right angles from the backbone down into the middle of the fillet.