The High Court in Wardley Australia Ltd v Western Australia [1992] HCA 55; (1992) 175 CLR 514 made it plain (at 533) that limitation questions of this kind should not generally be decided in interlocutory proceedings in advance of the hearing of the action.
It follows the Court must have the power to approve amendments to a writ or a pleading in such a case, notwithstanding it may be statute-barred. This is consistent with principle. When a statutory limitation bars the remedy rather [than] the right, the remedy is not barred unless pleaded in the defence (Ronex Properties Ltd v John Laing Constructions Ltd [1983] QB 398 at 405) and can be waived (Commonwealth v Verwayen (1990) 170 CLR 394.) Further, the grant of leave to amend in these circumstances cannot affect a defendant's rights pursuant to a statutory period of limitation.
The second issue is whether O 21 r 5(2) and (5) applies in this case. It will only do so if the relevant limitation period had not expired at the commencement of the action, but had expired by the time of making an application to amend to add a new cause of action.
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It appears to have been assumed for some time that the relation back doctrine as it applies to amendments to a writ and pleadings had the capacity to prejudice a defendant's rights under a statute of limitations in a situation where an action was commenced within the relevant limitation period and an application to amend was made after the expiry of the limitation period. The assumption explains the characterisation of the rule in Weldon v Neal [1887] 19 QBD 394 as a 'rule of practice'.
However, it is clear in Morgan v Banning (supra) that the rules of court cannot and O 21 r 5(5) does not give the Court the power to override or affect a defendant's accrued rights under a statute of limitations.
The purpose of O 21 r 5(5) is to avoid an overly technical and rigid investigation as to the degree of coincidence between the matters in the relevant pleading and those in the proposed amendment: Morgan v Banning per Owen J at 477.
Whether a new cause of action arises out of the same facts, or substantially the same facts, as the cause of action in respect of which relief has already been claimed is a matter of impression involving questions of degree: Dye v Griffin Coal Mining Co per Owen J at 434.