The Duchess of Cambridge will officially open a new treatment centre to help people to beat addiction.
Kate, who is Patron of the Action on Addiction charity - which runs the centre, will meet staff and people at different points of their recovery on a visit to the new community-based facility in Wickford, Essex.
She will also attend a special reception to mark the opening on Wednesday.
The centre, which opened its doors to clients last year, hosts a rolling cycle of nine-week long self-help addiction recovery programmes called Clouds in the Community.
The community-based programmes are described as an effective alternative to residential treatment and allow the charity to provide services in more places and to help more people.
Clouds in the Community serves as a starting point for long-term recovery and abstinence, leading to improvements in participants' physical and mental health and overall quality of life.
Action on Addiction said independent evaluation of its Essex programme showed almost 80% of clients did not return to any treatment service after completing the scheme.
The charity has several sites around the country, including its flagship Clouds House centre in Wiltshire which offers residential treatment, and a further community-based site in Liverpool.
It treats all forms of addiction including alcoholism, drug addiction, gambling addiction, sex addiction and food-related disorders.