The implied duty to cooperate under Secured Income is not required to be parsed through the BP Refinery (Westernport) five-factor test; the two doctrines have a common source in necessity but operate in distinct spheres. The content of the implied duty to cooperate is qualified by reasonableness — it requires a party to do what is 'reasonably necessary' to secure performance, not to do 'whatever it takes'. A party seeking to establish the content of an implied duty to cooperate in relation to contingent contractual obligations must adduce evidence of what was reasonable as at the date the relevant contractual terms were agreed, not with the benefit of hindsight.
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