Sir John Key believes the time was right to step down as chair of the country's biggest bank.

Key has been working with ANZ's Australian and New Zealand boards since 2017, and became chair in 2018.

He says the bank is in good shape and they had an obvious replacement in mind- so he knew he was ready to retire.

"The timing seemed about right for me, and it's a pretty good time for the bank as well."

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