The Queen has asked if "complacency" contributed to the financial crisis, during an informal conversation with Bank of England officials.
During her visit to the Bank, she also asked whether the Financial Services Authority (FSA) "did not have the teeth" to respond to the crisis.
The Queen was responding to a briefing by a member of the Bank's financial services committee.
The FSA said the regulatory system had been completely changed since 2008.
The Queen and the Duke of Edinburgh also toured vaults full of gold bars during their tour.
The couple also signed a million pound note each for the Bank's guest book and the Queen was shown the very first banknote she had signed on 29 November, 1937, aged 11.
Four years ago, during the height of the global crisis, the Queen had asked academics at the London School of Economics: "Why did nobody notice it?".
During this visit, Sujit Kapadia from the Bank's financial services committee gave the Queen three reasons why the crisis happened - one of which was that it was rare event which made it difficult to predict.
He added: "People thought markets were efficient, people thought regulation wasn't necessary. Because the economy was stable there was this growing complacency,"
'A bit lax'
"Thirdly, people didn't realise just how interconnected the system had become."
The Queen replied: "I suppose, in money terms, it is very difficult to foresee. But people had got a bit lax. Have they?"
When told that the officials in the room were there to prevent another crisis, the Duke jokingly asked: "Is there another one coming?"
A spokesman for the bank said: "The Bank of England is very grateful to Her Majesty for her visit today and for taking such an interest in its work."
The FSA also responded saying: "We've widely acknowledged that the regulatory approach before the financial crisis in 2008 was flawed and has since been completely changed.
"Parliament is now awaiting Royal Assent for the Financial Services Bill, which will determine the powers for the new regulators that will be created next year'"