The crew of a ferry on a short-term charter to the Interislander has been criticised for a briefly grounding near Tory Channel in 2011.
A Transport Accident Investigation Commission report has revealed the rudder of The Monte Stello was inadvertently turned in the wrong direction, causing the ship to glance off a rock.
No one was injured but its hull was indented and one of its two propellors was damaged.
The commission said the ferry bridge crews must follow its operating procedure to the letter and not leave anything to chance.
