Zaqia Crawford, an employee at the Christmas tree shop, told ET that at the time, she didn't realize she was waiting on Prince Harry and the Suits star.
"It was super casual. They were really nice," she explained. "It was one of those when you get a sale and you talk to really nice people and it's like, 'Ah, this is refreshing.' It was super casual. I had no clue."
"I didn't see any [security] unless they're like ninjas hiding in the trees," she added. "They just looked like two people chilling on a date who picked up a tree. They weren't overly affectionate, but you know that air you get when you know that you're dating? You got the vibe, but it wasn't mushy."
Zaqia revealed that the two selected a Nordmann Fir for £65, approximately $82.47.
"[Prince Harry] did shake my hand, which was kind of odd because I'm usually the one being overly affectionate to people," Zaqia continued. "[Meghan] was really dope. She was from America, so she heard my accent, I heard hers and I was like, 'Hey, where you from?' And she was like, 'Cali!'"
Others in the shop, like Zaqia's co-worker, Ollie Wilkinson, knew right away who they were serving.
"It was a big tree and we were struggling to get it through and then we looked up and realized that Zaqia had been serving this couple," he dished. "They'd picked their tree and when I looked up I realized it was Prince Harry. Zaqia's an American, so she didn't know who it was, so she was serving them. He was with his girlfriend. They were discussing America."
According to Ollie, Prince Harry, dressed casually in a winter hat, paid for the tree with Meghan by his side. "They asked how many trees we sold," he explained. "Then I gave them a bunch of mistletoe [and] they walked off holding hands with Harry carrying the tree."
"They seemed like they were getting on well," he added. "They walked off hand in hand and he was carrying a tree on his shoulder."
Sam Lyle, who co-founded the Christmas tree business with his brother, echoed those statements while chatting with The Mirror. "We have looked after some of Britain's highest profile names for nearly 20 years, but you could have heard a pin drop -- or a needle -- when Prince Harry and Meghan walked into the store," he said. "They were completely charming together and blissfully unaware that our jaws had hit the floor."
"We hope we can add them to our list of illustrious names who buy from us each and every year," he continued. "There would certainly be a rush from our staff should they ask us to decorate it too."
Meghan's trip to London comes a week after Prince Harry flew to Toronto, Canada, to visit the 35-year-old actress following his Caribbean Royal Tour. Royal expert Kate Nicholl told ET at the time that the two wanting to spend time together was understandable, as Meghan wouldn't be joining her beau for the holidays.
"[Harry] knows the rules of the royal family and he knows that until they get engaged, Meghan will not have a place around that Christmas dinner table," she explained. "If you think about all those years that Prince William was courting Kate Middleton, she had to wait 10 years until she was invited to Sandringham."
On Monday, ET caught up with Meghan's close pal, Priyanka Chopra, at UNICEF's 70th Anniversary event, where she discussed how the two keep in touch and the possibility of a royal wedding.
"I think whatever they need to know, she'll tell them. It's not my place to say," she said of Meghan and Prince Harry's relationship.
"Whatever relationship I share with her is completely private," she continued, adding that she and Meghan support each other by "answer[ing] my texts and pick[ing] up my phone."