The Duchess of Cambridge congratulated recovering addicts on their "inspiring" movies about the long path to sobriety at a film preview in central London.
Kate, who is patron of charity Action On Addiction, met the movie-makers from the Recovery Street Film Festival and heard stories about their battles.
The festival tours venues around the UK aiming to change perceptions and tackle the stigma surrounding the condition.
Wearing a floor-length white dress by Self Portrait, she sat in a theatre at Working Title Films' studios in Marylebone watching highlights of winning footage from the past three years.
Former addict David McCollom directed the 2016 winner Hope Inside and told the crowd about the people he had lost to drugs.
The Duchess thanked him for the "encouragement and inspiration" he had given people through his films.
He said: "I couldn't have written this - meeting royalty, it was incredible.
"If you had told me this when I was lying wrecked in hospital beds I would have told you that you were the one on something."
The festival was established three years ago by a consortium of addiction charities, including Action On Addiction.
The Duchess watched three prize-winning films.
They were Harry's Story, which explores addiction's connection to mental health; Understanding Mum, which reflects on parental substance abuse; and Hope Inside, which discusses recovery in prison.
Graham Beech, chief executive of Action On Addiction, said the festival shows sufferers can live "a life of freedom" from the "harsh realities" of drug abuse.
Kate made the visit before going to the world premiere of a film about a homeless man's relationship with his feline friend, called A Street Cat Named Bob.