The last poignant photograph of Thomas Kingston with his wife, Lady Gabriella, was taken on Valentine's Day.
The smiling, happy couple joined Queen Camilla and Lady Gabriella's brother and his wife, Lord and Lady Frederick Windsor, at a star-studded event in London to celebrate the work of William Shakespeare.
The royals witnessed performances by Dame Judi Dench, Gary Oldman and Robert Lindsay at Grosvenor House.
Lady Gabriella looked elegant in a cobalt blue pussy-bow blouse and a navy satin skirt for the occasion, while Thomas matched his wife by wearing a bright blue scarf.
Thomas was a financier who married into the royal family after a summer proposal on the island of Sark almost six years ago.
He died suddenly at the age of 45 on Sunday, Buckingham Palace announced on Tuesday evening.
Mr Kingston, known as Tom, was found dead at an address in Gloucestershire on Sunday evening, and emergency services were called to the scene shortly after 6pm.
Lady Gabriella paid tribute to her husband in a joint statement with his family, describing him as an "exceptional man who lit up the lives of all who knew him".
The couple had been set to celebrate their fifth wedding anniversary this spring.
After getting engaged in August 2018, Lady Gabriella and Thomas married at St George's Chapel, Windsor Castle on 18 May 2019.
The bride, who is the daughter of Prince and Princess of Kent, wore a lace wedding dress by Luisa Beccaria.
Lady Gabriella, who is not a working member of the royal family, is a writer and contributing editor.
She is also a singer-songwriter and released two bossa-nova inspired tracks in 2020 to raise money for charity.
Earlier on Tuesday, her parents, Prince and Princess Michael of Kent, put on a brave face as they attended a thanksgiving service for the late King Constantine, the last king of Greece, in Windsor.
No funeral plans have been released so far.