The Duchess wore a Temperley London lace dress to mark World Mental Health Day.
Chong will open his first stand-alone store on Albemarle Street in London’s Mayfair by December.
Kensington Palace released a statement to confirm the news.
The portrait was photographed by Chris Jackson — the husband of Kate Middleton’s personal assistant Natasha Archer — in June at Kensington Palace.
The trip is part of a European tour on behalf of Britain’s Foreign and Commonwealth Office.
The duchess made her first trip to Wimbledon as royal patron of the All England Lawn Tennis and Croquet Club.
She was there for a tour of the V&A’s new Exhibition Road Quarter, which comprises a vast new courtyard and underground gallery designed by the British architect Amanda Levete and her company AL-A.
A patron of the 1851 Trust, she took part in the charity’s Land Rover Bar Roadshow held at the Docklands Sailing and Watersports Centre.
She wore a navy tweed Rebecca Taylor skirt suit.