13 In my view the appellant (defendant) should have pleaded the provisions of Pt IV Div 2 of the Act, or any other statutory provision or point of law, upon which it relies for its assertion that the respondent's (plaintiff's) claim is not maintainable. It is not to the point that the decision in Dutch (supra) was only given after the original defence in this action was drawn and filed because it has always been open for the appellant (defendant) to apply for leave to amend its defence to plead these grounds - RSC O 20 r 10. One of the principal functions of pleadings is for the parties to identify those issues which are in contest in the proceedings and which, therefore, require a decision by the court. The failure of a party to plead a particular issue, for example a conventional limitation provision, will mean that such a defence cannot be relied upon by the party who should have raised it in its pleading - Teague v Jones (supra). Furthermore, the obligation upon the party relying upon such a special defence to plead it, also allows the opposing party to respond to that plea, whether by way of reply or subsequent pleadings by leave, thus enabling any relevant issue to be identified which may be an answer to that special plea or render it unavailable. Obvious examples may be waiver, or estoppel. Whether such pleas would be capable of providing an answer to this proposed defence, or whether indeed there is any answer to such a defence, does not arise in the present case. Perhaps the existence of an irrefutable defence, which the appellant asserts occurs in the present circumstances, is the best of all reasons to insist that it be specifically pleaded so that it will come to the notice of the opposing party and the court at the earliest opportunity. Such a plea may be sufficient to cause the opposing party to abandon the action without any determination by the court or, failing that, may allow the action to be disposed of by a final judgment on a point of law or by some other summary procedure.