The Duchess of Cambridge, 38, attended a special performance of the musical "Dear Evan Hansen" at the Noel Coward Theatre in London with husband Prince William.
For the outing, the mom of three opted for a three-quarter sleeve dress by Eponine as well as sparkly Jimmy Choo heels and a matching clutch, according to People. Per the outlet, Middleton's diamond chandelier earrings are from the queen.
Middleton -- who has previously borrowed Queen Elizabeth's jewelry -- has worn this pair of earrings to multiple outings, including in 2011 for a British Academy Film Awards dinner in Los Angeles, as well as the 2017 Variety Performance and the Tusk Conservation Awards in 2018, according to People.
In a post on the Cambridges' official Instagram page, it was explained that the event was held on behalf of The Royal Foundation.
"The musical @dearevanhansen has been credited with helping to start important conversations about mental health between parents and teenagers," the statement read.
It continued: "The issue of mental health is a key priority for The Royal Foundation which works to tackle the stigma and encourage more people to talk openly about their mental health."
"@GiveUsAShoutInsta, a free and confidential 24/7 UK text messaging helpline that supports people in crisis and was developed by The Royal Foundation, is one of four not-for-profit partners of the show which provide mental health resources to audiences and beyond," the statement concluded.