Lord Nicholls in Inco Europe Ltd v First Choice Distribution

A court may add to, omit, or substitute words in a statute to correct an obvious drafting error only where it is abundantly sure of (1) the intended purpose of the provision, (2) that the draftsman and Parliament inadvertently failed to give effect to that purpose, and (3) the substance (though not necessarily the precise words) of what Parliament would have enacted had the error been noticed.