To strengthen argument: According to T 1742/12, an invention that would have been obvious starting from a document in another field does not become inventive merely because a “closer” document exists. Remoteness alone does not disqualify a document from being a valid starting point, provided the reasoning is not hindsight-driven.
Here, D5 provides the decisive teaching for solving the same problem, and the skilled person could apply it using routine adaptation. Therefore, D5 represents a plausible springboard for assessing inventive step, consistent with CLBA I.D.3.2 (2025) and the principle that any art can serve as CPA if it logically leads to the claimed subject-matter.