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Contract law help on the doctrine of good faith

Hi, I'm currently working on my contract law essay which was to critically discuss the statement made by Justice Leggatt in the case of Yam Seng Pte Limited v International Trade Corporation Limited [2013]

"Under English law a duty of good faith is implied by law as an incident of certain categories of contract, for example contracts of employment and contracts between partners whose relationship is characterised as a fiduciary one. I doubt that English law has reached the stage,however, where it is ready to recognise a requirement of good faith as a duty implied by law, even as a default rule, into all commercial contracts. Nevertheless, there seems to me to be no difficulty, following the established methodology of English law for the implication of terms in fact, in implying such a duty in any ordinary commercial contract based on the presumed intention of the parties."

I understand that good faith isn't a doctrine normally applied by the courts in contract law cases but what does the above statement essentially mean?
Any help would be greatly appreciated, thank you!