Michelle Obama has said the Queen branded royal protocol "rubbish" when they met during a visit to Windsor Castle.
The former First Lady said she was panicking about following the rules of behaviour ahead of being greeted by the monarch.
The Queen collected her and Barack Obama from their helicopter during their last visit of his presidency.
Recalling the moment, Mrs Obama said she had been briefed on protocol which was then “buzzing round my head”.
Speaking during a Q&A session with author Chimamanda Ngozi Adichie on Monday, she said: "This is just how it feels to be at these high levels where people are talking protocol to protocol, that is how these big foreign exchanges are.
"People are talking to other people and then you're briefed and you're told 'this is going to happen and don't stand there and don't touch there and this is precisely what is going on'.
"This was on our last visit and we went to Windsor Castle and we took Marine One, the helicopter, and we landed in a field and we were going to be driven by the Queen and picked up in the car.
"Our Secret Service doesn't even let me ride around with Malia so up until that point we had never driven in a car driven by anyone else, so it was like 'this is what's going to happen, you're going to get out and sit here and this is what is going to happen'.
"Of course your head is spinning because first of all I'm trying not to fall, which is a major thing that I think about in public. If you're thinking about my thoughts when I come out on stage it's 'don't' fall'. One of my primary goals for the eight years was to never become a meme.
"So I had all this protocol buzzing in my head and I was like 'don't trip down the stairs and don't touch anybody, whatever you do' and so the Queen says 'just get in, sit wherever' and she's telling you one thing and you're remembering protocol and she says 'Oh it's all rubbish, just get in'.
Mrs Obama also recalled the controversy she caused when she touched the Queen’s back during a separate visit.
She said: "I touched her. After all those protocol lessons, I was human."
Mrs Obama added that her husband had always had a great affection for the Queen, saying: "Barack is so incredibly fond of Her Majesty and I won't go into his fangirling but I think it's because she does remind him of his grandmother Toot, she's smart and funny and honest. He is a huge fan for sure."
Tickets for the London event, which is part of an international book tour, sold out quickly and the audience included actor Riz Ahmed, actress Michaela Coel and model and activist Adwoa Aboah, as well as Mayor of London Sadiq Khan and 300 school children from secondary schools in Lambeth and around the UK.
