he plausibility test requires that all valid patents make a technical contribution which is at least plausible. Plausibility originates in the case law of the European Patent Office (EPO) but has been most enthusiastically embraced by the UK courts such that it finds application across virtually all grounds of revocation. Although lacking a legislative basis, plausibility is rationalised on the grounds that "the patent monopoly should correspond to and be justified by the technical contribution to the art". [---] Adopting this approach would bring greater coherency to the law, and recognise plausibility as a true conditio sine qua non of the patent system.