On a sunny, if humid, Tuesday morning in Sydney earlier this month, Commonwealth Bank began emailing about a million customers to tell them it was switching them into a different savings account. One that would, controversially, charge a $3 fee each time they withdrew their money over-the-counter at a branch.

Angus Sullivan, the head of CBA’s market-leading retail division, had figured this was an innocuous change. Cash use is falling, and most customers prefer to use ATMs to get their money than visit a branch.