An act done by a statutory authority falls within the first limb of a 'pursuant to' statutory immunity provision if it falls within a broad description of authorised acts in the statute (such as 'any reasonable measure'), even if not specifically listed. The word 'reasonable' in such a broad empowering provision bears a Wednesbury sense, not a common law negligence sense, so that conduct may be negligent at common law yet still be a 'reasonable measure' for the purposes of the statutory power and thus attract immunity. A finding of breach of common law duty of care is in no sense probative of Wednesbury unreasonableness.
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