It would make a good pub quiz question: what was the most costly bailout of the 2008 financial crisis? Royal Bank of Scotland? Citigroup? Many assume so. Of course, the biggest failure of them all was not a bank at all, but insurer AIG.

In total, AIG needed $182bn of bailout money from the US government – more than twice as much as the next biggest casualty, RBS – although by last year, like most of the American bailout cases, the federal investment had turned a profit. The fact remains, however, that the biggest financial sector collapse in the history of capitalism was a group that was nominally an insurer, but one that diversified so fast that it became impossible to manage or regulate.

In the aftermath of the financial crisis, politicians, regulators and the general public have focused almost obsessively on the banks. But the recent troubles of Britain’s RSA – five years after AIG’s disastrous collapse – are a useful reminder that insurers need watching, too.