Action on Addiction chief executive Nick Barton welcomed Kate Middleton to Hope House after defending her against controversial criticism made by author Hilary Mantel.
Booker Prize-winning author Hilary had described Kate has having no personality and a "perfect plastic smile".
Nick disagrees with Hilary's description. "I can only speak of what I know, and having met the Duchess several times I find her to be engaging, natural and genuinely interested in the subject," he said.
"You can tell a lot about someone from the questions they ask and she asks really good questions, the questions of someone who wants to learn. She is also an intelligent woman." Nick says that Kate's support of his charity is invaluable. " We are thrilled that the Duchess will be supporting us in our mission to free people from addiction and its effects," he has said.
Her visit will have also given the female residents of Hope House a much-needed boost. Hope House in Clapham, south London, is a 22-bed residential centre for women battling addictions to drink and drugs.
Amanda Thompson, research manager at Action on Addiction, predicted that Kate would find the visit emotional. "The Duchess has a heart and will certainly find it moving - it's impossible not to cry," she said. "These are heart-rending tales of what they have been through. It's a gritty issue - it will be an emotional day."
Kate had chosen to support this charity because she felt that addiction "lay at the heart of many of the social issues she was looking at," a source was quoted as saying.
Before being announced as Patron, she paid a private visit to a treatment centre and "spoke at length to a number of clients about their addiction and personal journeys to recovery."