As fans can recall, during a visit with President Barack Obama to Buckingham Palace in 2009, the former first lady placed her arm around the monarch.
"Yikes! Sorry guys," Obama, 55, joked during the London portion of her "Becoming" book tour on Sunday.
When asked if she would have done anything differently at that moment 10 years ago, Obama explained that she doesn't think she could have.
"What is true among world leaders is that there are people who handle protocol, and usually the people they're representing don't want all that protocol," she said (via the Daily Mail).
"So you wonder, well who are you doing this for because they don't want it, we don't want it," Obama continued. "But it's just the way things are. So I don't know that I could have done anything differently because it was a natural human reaction."
At the time, a smiling Queen Elizabeth also strayed slightly from protocol and briefly wrapped her arm around Obama in a rare public show of affection. It was the first time Obama had met the queen.
A Buckingham Palace spokesman, who asked not to be identified because of palace policy, previously said he could not remember the last time the queen had displayed such public affection with a first lady or dignitary.
"It was a mutual and spontaneous display of affection," he said. "We don't issue instructions on not touching the queen."
In her memoir "Becoming," Obama also wrote about the occurrence, reiterating that she did what was "instinctive" to her.
“Forget that she sometimes wore a diamond crown and that I’d flown to London on the presidential jet: we were just two tired ladies oppressed by our shoes,” Obama said (via HuffPost). “I then did what’s instinctive to me anytime I feel connected to a new person, which is to express my feelings outwardly. I laid a hand affectionately across her shoulder."
She continued: "But I tried not to let the criticism rattle me. If I hadn’t done the proper thing at Buckingham Palace, I had at least done the human thing. I daresay that the Queen was okay with it, too, because when I touched her, she only pulled closer, resting a gloved hand lightly on the small of my back.”
The Associated Press contributed to this report.