President Donald Trump may have broken royal protocol on Monday when he appeared to lightly touch Queen Elizabeth II during the state-banquet dinner amid his UK visit.

Royal protocol dictates that one must not touch the queen unless she offers her hand first.

Former first lady Michelle Obama violated this rule in 2009 when she hugged the queen during a visit to the UK.

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When you're a world leader in the company of an English monarch, you can look but you can't touch.

President Donald Trump on Monday appeared to lightly touch Queen Elizabeth II on the back during the state banquet as he visited the UK, which is a violation of royal protocol.

In order to touch the queen, protocol dictates that she must first offer her hand to you.

Former first lady Michelle Obama broke this rule in 2009, and it appears Trump has done the same a decade later.

Obama in 2009 went as far as to hug the Queen, which she later characterized as an "epic faux pas."

Describing the moment in her 2018 memoir, "Becoming," the former first lady wrote, "Forget that she sometimes wore a diamond crown and that I'd flown to London on a presidential jet; we were two tired ladies oppressed by our shoes. 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."

Read more: 8 ways Trump could offend the Queen during his state visit to the UK

At the time, the queen seemed to allow this break in protocol and returned the gesture.

The queen did not react in a noticeable way when Trump appeared to touch her on Monday. The White House did not immediately respond to a request for comment from INSIDER.