Led by the Forward Trust, “Taking Action on Addiction” is a long-term campaign which will work to improve awareness of addiction. Kate Middleton, who stunned in a red turtle neck jumper and matching pleated skirt, is patron of The Forward Trust.
TV presenters including Ant and Dec will also attend the event.
Kate, who become patron of the Forward Trust in June, will deliver a keynote address launching the campaign.
The launch coincides with Addiction Awareness Week, running from October 18 to October 24.
Throughout her years as Duchess, Kate has worked with several addiction charities, which has informed much of her work on early years education.
Kate went for minimal jewellery, with her huge sapphire engagement ring on show.
The Duchess added a pair of simple gold earrings to the look which could be seen underneath her hair.
The complete the look, Kate recycled her favourite DeMellier bag in tan along with a matching pair of tan heels.
The bag retails for £295 and boasts a modern, triangle shape, complete with a tubular rigid top handle.
Taking to social media to share their thoughts on the look, royal fans were delighted to see Kate out.
Instagram user Diane Turkington said: “The sheer elegance of our future Queen.”
Sienna Matlock wrote: “Absolutely stunning, she never fails.”
One fan account said: “She looks splendid and elegant.”