Catherine, Duchess of Cambridge visits Hope House, an Action on Addiction women's treatment centre on February 19, 2013 in London, England. Credit: Neil Mockford/FilmMagic

Royal baby on board! On Tuesday, Feb. 19, Kate Middleton  made her second official public appearance since announcing her pregnancy in December 2012. The Duchess of Cambridge visited women recovering from addiction at Hope House, Action on Addiction, in London.

Fresh off her babymoon in Mustique with Prince William, the 31-year-old brunette looked tanned and healthy wearing a MaxMara dress. "It's lovely to be here," she said after arriving at 11:30 a.m. local time.

Middleton's outing comes just after English novelist Hilary Mantel called her a "shop window mannequin" with a "plastic smile." The Bring Up The Bodies author also described the mom-to-be as a "painfully thin" woman "without quirks, without oddities, without the risk of the emergence of character." (See more photos of pregnant Kate Middleton!)

Nick Barton, chief executive of Action on Addiction, defended Middleton during her visit. "I've met her several times and I found her to be engaging. I found her very natural," he told reporters. "I found her actually genuinely interested in the subject."

Barton added, "You can tell a lot from people's questions and she asks really good questions. They're not routine stuff, they're questions of someone who wants to learn. I find her very easy to deal with."

Middleton became a patron of Action on Addiction in January 2012. "Having her as patron of the charity draws attention to the cause of addiction as a whole, which is not always an easy subject," Barton said. "She is doing an enormous amount to reduce the stigma of addiction and increase understanding of it."