Catherine, Duchess of Cambridge attends the official opening of The Natural History Museums's Treasures Gallery at Natural History Museum on November 27, 2012 in London, England. Credit: Samir Hussein/

One grande decaf skinny latte for the Duchess, pronto! Last Friday, Jan. 11, a pregnant Kate Middleton quietly emerged from Kensington Palace for a very hush-hush jaunt: A walk through Kensington Gardens with dog Lupo followed by a drop-in at a nearby Starbucks!

Escorted by a security guard, the 31-year-old Duchess "looked beautiful," an onlooker tells Us Weekly. "Her hair was done nicely and she had a scarf, lovely long coat and boots on." Still under wraps, although Middleton is now in her second trimester? Her baby bump. "She was wrapped up warm, so I couldn't see the bump," the observer explains.

As the security guard waited outside with Lupo, Prince William's wife went inside and placed her order herself: Her decaf drink, plus a cookie. "Kate was smiling," the observer continues, adding that she "paid with a Starbucks card, which she swiped herself."

Thus armed with provisions, the expectant royal took Lupo's leash back from the security guard (the pooch is "so cute and well-behaved," the spy says), and the trio continued on their walk.

"She's a regular," a Starbucks staffer tells Us of the unassuming Duchess. This past Monday, she and William, 30, announced they "are delighted to confirm they are expecting a baby in July," adding that "The Duchess's condition continues to improve since her stay in hospital last month." (Middleton's first trimester was marred by acute morning sickness.)