The UK-IPO now uses the „Aerotel/Macrossan“ test to determine if an invention is patentable. This test is different from the approach developed by the EPO but the two approaches should generally give the same answer.1)
Stage 1: construction
You first have to decide what the monopoly is before going on the question of whether it is excluded.
Stage 2: Identify the contribution
This step is an exercise in judgment probably involving the problem said to be solved, how the invention works, what its advantages are. What has the inventor really added to human knowledge perhaps best sums up the exercise.
Stage 3: Is that solely excluded matter?
This step is merely an expression of the „as such“ qualification of Art.52(3).
Stage 4: Check whether the contribution is „technical“
This step may not be necessary because the third step should have covered that.