Gordon Brown has admitted he was left "embarrassed" after private meetings with the Queen as she often knew more than he did about current affairs.
The Labour grandee, who was Prime Minister between 2007 and 2010, said the monarch "actually knew better about what was happening to the country" than he did during his time in No10.
Mr Brown, who was among the 15 PMs who served during the Queen's 70-year reign, said she never gave him advice during their weekly meetings but showed a keen interest in the events of the day.
In an interview with the BBC, he recalled how the Queen questioned "why have these bankers got it all wrong" in 2008, when the financial crash led to the UK entering recession.
He said: "She would listen, she would ask questions. She would be endlessly knowledgeable about everything happening in the Commonwealth.
"I was very embarrassed one day because I went in to see her at six o'clock, I didn't know that one of the Commonwealth leaders had been ousted and a new government had been formed.
"She was telling me what was happening when I was supposed to report to her."
Mr Brown, who was at Saturday's Accession Council meeting where Charles III was formally declared as the new King, said the Queen could even be better informed than he was on events in this country.
He said he could have been "in the House of Commons all afternoon, in endless debates or cabinet meetings or something" while he said the Queen had been keeping herself up to date by watching television and would be "getting notes from her secretaries".
He added: "She actually knew better about what was happening to the country than I was. It was quite embarrassing.
"It just showed how conscientious she was, how well up on the detail, I think right to the last.
"You could see that in the meeting she had with Liz Truss when she became Prime Minister and Boris Johnson when he left, she could perform the duties right up until the end.
"She listened and she asked questions. I remember famously she asked 'why have these bankers got it all wrong?' in 2008."
However, he stressed the Queen would "never impose her will" on the Prime Minister.
"This is the modern monarchy and I think she set the tone for what King Charles and the other monarchs will do," he said.
Mr Brown also joked about how the Queen once told her corgis to "shut up" in front of his young sons.
He said his children would defend themselves when being told off for using the phrase by saying: "If the Queen says it, why can't we?"
