Sir Rod Stewart was a fan of King Charles' recent state visit to the United States to summit with President Donald Trump, and did not mince words congratulating the British monarch on Monday during The King's Trust 50th anniversary celebration in London.

According to Consequence, the "Maggie May" singer told Charles, "May I say well done in the Americas. You were superb. Absolutely superb. You put that little rat bag in his place…"

The awkward kudos apparently caused Charles to chuckle.

The monarch entertained a line-up of celebrity guests at the event, including Stewart and The Rolling Stones guitarist Ronnie Wood.

Since Charles launched the charity in 1976, The King's Trust has helped over 1.3 million young people access education, employment and training.

During the monarch's visit to the U.S. last month, Charles reminded Trump that America might be "speaking French" if not for the British and spoke of the "indispensable alliance" between the U.S. and the United Kingdom.

Charles also stressed the importance of the North Atlantic Trade Organization, a topic Stewart feels strongly about. Earlier this year, the raspy British singer posted a video on social media criticizing Trump after he questioned the courage of NATO troops who served in Afghanistan.

Stewart was a longtime friend of Trump's and the two appeared friendly at many events throughout the years, but Stewart is said to have ended their friendship over Trump's alliance with Israel.