Few abominations can compare with a ‘motoring leech’, but the leech line should really be the last resort in subduing the horror. If you over-tighten the line, it will end up by ‘hooking’ the leech of the sail and ruining the clean airflow off its trailing edge. Before attending to the leech line, first make sure the sheet’s fairlead car is correctly set in its fore-and-aft position; now ease the line until it is slack, then carefully pull it down until the leech goes quiet, AND NOT AN INCH MORE.

If you have had to give a reefed mainsail a touch of leech-line, don’t forget to let it off as you shake out the reef.