What is the test evolved by Holmann J. to decide whether a variant infringes an invention?

The test evolved by Holmann J. to decide whether a variant infringes an invention is commonly referred to as the "Improver" or "Protocol" test. This test was established in the UK patent law case Improver Corporation v. Remington Consumer Products Ltd. [1990] FSR 181.

The Improver test aims to determine whether a variant of a patented invention infringes on the patent holder's rights. It provides a structured approach for courts to assess whether a product or process that differs from the patented invention in certain respects still falls within the scope of the patent's claims.

The key elements of the Improver test are as follows:

1. The Essential Features of the Invention:
   The court first identifies the essential features or "pith and marrow" of the patented invention. These are the core elements or characteristics that define the inventive concept and distinguish the patented invention from prior art.

2. The Nature of the Variant:
   Next, the court examines the nature of the variant in question. This involves analyzing the differences between the variant and the patented invention, including any modifications, adaptations, or substitutions made to the essential features of the invention.

3. The Purpose or Effect of the Variant:
   The court then considers the purpose or effect of the variant. It assesses whether the variant achieves substantially the same result as the patented invention, either in the same way or in a manner that is immaterial to the inventive concept.

4. Obviousness of the Variant:
   The court evaluates whether the variant would have been obvious to a person skilled in the art at the time of the invention. This involves assessing whether the variant would have been an obvious development or alternative solution based on the state of the art and common general knowledge in the relevant field.

5. The Improver Question:
   Finally, the court poses what is known as the "Improver question," which seeks to determine whether the variant falls within the scope of the patent's claims by achieving substantially the same result as the patented invention in a manner that is not substantially different from what was envisaged by the patentee.

The Improver test provides a flexible framework for courts to assess patent infringement cases involving variants or modifications of patented inventions. It recognizes that patent protection should extend beyond literal infringement to cover functionally equivalent variations that embody the same inventive concept. By applying the Improver test, courts can ensure that patent holders' rights are adequately protected while also promoting innovation and technological progress.