The “fit and proper” test is regulators’ and professional associations’ tool of choice for assessing suitability for office – a spirit-level for acceptable conduct.

This month, for instance, the UK’s Financial Services Authority used it against banker Peter Cummings. The watchdog banned him for life from high finance and said he had encouraged a “culture of optimism” at HBOS’s corporate lending division that had helped bring the bank down.

But is the “fit and proper” test itself fit for purpose? While everyone agrees these are qualities business leaders should have, few can agree precisely what those terms mean. Even the central bank for central banks – the Bank for International Settlements – says “the assessment of fitness, propriety and other qualifications is a judgmental matter” and suggests bank supervisors may have to work it out on a case-by-case basis. US legislators lowered the threshold to disqualify company directors from “substantial unfitness” to mere “unfitness” after a rash of corporate scandals 10 years ago, but courts still wrangle over the definition.