JUDGMENT

Raus Sharif CJ:

Introduction

[1] The present appeal concerns the validity of a patent relating to a plumbing product known as the SPIND Floor Gully/Trap. The appellant brought an action for, inter alia, infringement of the patent against the respondents. The respondents filed a counterclaim seeking a declaration that the patent is invalid.

[2] On 27 November 2014, the High Court dismissed the appellant's claim and allowed the respondents' counterclaim.

[3] On 22 March 2016, the appellant's appeal was unanimously dismissed by the Court of Appeal.

[4] Leave to appeal was granted by this court on 20 July 2016 in respect of the following questions of law:

(i) Whether for the purpose of considering whether a patented invention is inventive (or not obvious), the court is required to apply and carry out the four-step test from the case of Windsurfing International Inc v. Tabur Marine (Great Britain) Ltd [1985] RPC 59 (or more commonly known as the Windsurfing test ), ie the first is to identify the inventive concept embodied in the patent in suit. Thereafter, the court has to assume the mantle of the normally skilled but unimaginative addressee in the art at the priority date and to impute to him what was, at that date, common general knowledge in the art in question. The third step is to identify what, if any, differences exist between the matter cited as being "known or used" and the alleged invention. Finally, the court has