LONDON—Saying the first lady’s skills were of the highest caliber he’d ever witnessed, Buckingham Palace guard Robert Addington told reporters Thursday that he was impressed by Melania Trump’s ability to never crack a smile on her visit to London. “There were all sorts of people waving in her face and yelling things at her, hoping that she would break, but she managed to hold that same stern, emotionless expression the entire time. It was incredible,” said Addington, who was in awe over how, even when Prime Minister Theresa May attempted to make Melania Trump laugh or smile with a joke or by giving her a compliment, not one single muscle moved in the first lady’s face. “Sentries go through months of training to maintain that kind stoicism, and Mrs. Trump’s abilities just blow us out of the water; she’s a natural. It’s inspiring. Even when the president put his arm around her at one point to take a photo, she didn’t flinch. If anything, she just became even more detached.” Addington, who said that there was one point where he almost thought he saw Mrs. Trump relax into a smile after the President walked several feet away from her, acknowledged that it was just his eyes playing tricks on him.