An expert in bank regulation says Ireland's bank guarantee was "the stupidest own-goal in history".

However, Professor Bill Black says he understands why politicians made the decisions they did.

He's told the inquiry that Ireland had a situation where banks and regulators were "BFFs" - or 'best friends forever'.

But he says that was a recipe for disaster - and the entire country was let down as a result:

You can watch the banking inquiry live here.