The world's tentative experiment with negative interest rates got off to an unremarkable start.

Sweden's Riksbank - the world's oldest central bank - became the first major monetary authority to cross the rubicon and take its main policy rate into the red exactly a year ago to the month.

The Riksbank's move followed the likes of Switzerland and Denmark, who had turned negative in a bid to stimulate flagging inflation and halt the punishing appreciation of their currencies.

But sub-zero rates did not cause immediate panic in financial markets that central bankers were "losing control".

Neither did they seem to produce any deleterious economic effects in their host countries, as savers continued to keep their money deposited in banks rather than fleeing for the safety of cash. Commercial lenders, meanwhile, adjusted their business models to help maintain profitability.

• How Sweden's negative rates turned economics on its head

In September, Andy Haldane, chief economist at the Bank of England, joined a chorus of influential thinkers when he posited that negative rates could be necessary to protect the UK and the other advanced economies from the next global recession.

The "new abnormal"

But recessionary fears have crept up on the world much faster than the likes of Mr Haldane may have anticipated at the end of last year.

• Why this market crash is like nothing we've seen before

Global markets have crashed into bear market territory. A cocktail of fears over the collapsing price of oil, the creaking health of the world's biggest banks and China's competence in managing its economic slowdown, has sparked fears that investor panic may lead the world into a new downturn.

Bank shares have been in the eye of the selling storm and have concentrated minds on just what negative interest rates mean for the financial system.