Farewell Aerotel, It's Been Emotional

In its recent decision in Emotional Perception AI Limited v Comptroller General of Patents, Designs and Trade Marks [2026] UKSC 3 [↗], the UK Supreme Court has overturned the long-standing "Aerotel" test for how excluded subject-matter, such as computer programs, is assessed in the UK.

Background

The Aerotel test was set out by the Court of Appeal almost 20 years ago, in their judgment of Aerotel Ltd v Telco Holdings Ltd [2006] EWCA Civ 1371 [↗]. It has been binding on the Court of Appeal and all lower courts, as well as the UK Intellectual Property Office (UKIPO), since - with the Supreme Court being the only court able to overrule previous decisions of the Court of Appeal.

The present appeal to the Supreme Court concerned a patent application [↗] for an AI system designed to recommend files (e.g. media files) based on the emotional response that they are likely to elicit from the user. The invention makes use of an Artificial Neural Network ("ANN") that is trained to determine the subjective or emotional human perception of the similarity between different files based on the objectively measurable physical properties of those files.

This application was refused in June 2022 by a decision BL O/542/22 [↗] following a hearing at the UKIPO. In this decision, the hearing officer rejected the application on the basis that the claimed subject-matter was determined to relate to a computer program "as such" and therefore excluded from patentability under Section 1(2) of the UK Patents Act 1977 (UKPA) [↗].

This decision sparked a series of appeals through the UK courts, before finally reaching the Supreme Court, for its decision on three key issues, namely: (1) whether the Aerotel test should continue to be followed; (2) whether an ANN is (or contains) a computer program; and (3) if so, whether an ANN is a computer program "as such".

Issue 1: Rejection of the Aerotel test

In deciding on the first issue, the Supreme Court has decided that the Aerotel test should no longer be followed by the UK courts and the UKIPO. This is to bring the UK's approach to assessing excluded subject-matter in line with recent decisions of the Enlarged Board of Appeal of the European Patent Office (EPO) regarding the corresponding provision of Article 52 [↗] of the European Patent Convention (EPC) - most notably G1/19 [↗]. Specifically, the Court decided that the existing Aerotel test was not compatible with the interpretation of the EPC as determined by the EPO's Enlarged Board of Appeal in various cases.

In the place of the previous Aerotel test, the Supreme Court has decided that UK courts will now adopt the "any hardware" test that is used at the European Patent Office (EPO). This test presents a much lower bar for applicants to satisfy. In essence, for computer software, this test can be satisfied by including an indication in the claims that the operations described are to be performed on a computer (the "hardware").

The Supreme Court also confirmed that this replacement of the Aerotel test did not invalidate the UK's existing "Pozzoli" test for inventive step. Nonetheless, it did identify the necessity for an "intermediate step" to be carried out prior to the assessment of inventive step following the determination, under the "any hardware" test, that the claimed invention is not excluded from patentability under Section 1(2) UKPA. This intermediate step is needed to determine which features of a mixed invention (i.e. one which includes a combination of technical and non-technical features) contribute to its technical character - thereby allowing "non-technical features as such" to be excluded from the assessment of inventive step. On this point, it is noted that non-technical features which do interact with the technical subject matter of the claim, which are therefore not non-technical features "as such", are to be included in the assessment of inventive step. However, despite identifying the need for an "intermediate step", the Supreme Court refrained from prescribing how such analysis should be conducted.

Issues 2 & 3: ANNs are Computer Programs (but, in this case, not "as such")

On the second issue, the Supreme Court held that an ANN is a program for a computer. The Court reasoned that an ANN constitutes, in essence, a set of instructions to manipulate data in a particular way so as to produce a desired result - which is the defining characteristic of a computer program, regardless of how it is implemented in hardware.

On the third issue, the Court held that, although an ANN is a computer program, the claims (of the application under consideration) included various technical means, including (implicitly) some form of computer hardware since that would be required to implement the ANN. Under the new "any hardware" test, that is sufficient to bring the claimed invention within patentable subject matter. The Supreme Court therefore held that the UKIPO was wrong to refuse the application on excluded subject-matter grounds, and remitted it back to the UKIPO for further examination on inventive step.

The Most Significant Bit

This decision represents a significant shift in UK patent practice and introduces some uncertainty. In particular, it remains to be seen how the UKIPO and lower courts will integrate this new "any hardware" test with the existing "Pozzoli" test for inventive step - a question that is currently the subject of much interest and discussion among legal professionals.

However, in my opinion, despite this uncertainty, I do not believe that this decision will ultimately lead to much change in the types of inventions for which patents can ultimately be obtained. Instead, I suspect, the grounds under which applications which would have been refused as relating to excluded subject-matter are refused will simply shift to inventive step instead - with applications for inventions relating to software that provides an additional technical effect (beyond the mere execution of a program by a computer) continuing to be allowable.