Lady Gabriella Kingston's husband, Thomas Kingston, has died at the age of 45, Buckingham Palace announced on Tuesday.
In a statement released on behalf of Lady Gabriella, Mr Martin and Mrs Jill Kingston, Mrs Joanna Connolly and Mrs Emma Murray read: "It is with the deepest sorrow that we announce the death of Thomas Kingston, our beloved husband, son and brother. Tom was an exceptional man who lit up the lives of all who knew him. His death has come as a great shock to the whole family and we ask you to respect our privacy as we mourn his passing."
A Palace spokesperson said: "The King and The Queen have been informed of Thomas’s death and join Prince and Princess Michael of Kent and all those who knew him in grieving a much-loved member of the family. In particular, Their Majesties send their most heartfelt thoughts and prayers to Gabriella and to all the Kingston family."
Mr Kingston was found deceased at an address in Gloucestershire on Sunday evening. Emergency services were called to the scene shortly after 6pm. An inquest will be held to establish the cause of death but there are no suspicious circumstances and no other parties involved.
Gloucestershire Police said in a statement: "We were called by the ambulance service at 6.25pm on Sunday with a report of the death of a 45-year-old man at an address in the Cotswolds. The death is not being treated as suspicious and a file will be prepared for the coroner."
Lady Gabriella, 42, who is a British writer, wed financier Thomas in May 2019 at St George's Chapel in Windsor.
Thomas was a director of Devonport Capital, which specialises in providing finance for companies in "frontier economies". The Bristol University graduate had also worked in Baghdad, Iraq, working to procure the release of hostages after joining the Diplomatic Missions Unit of the Foreign Office.
Prince Michael and Princess Michael of Kent were among the royals to attend a thanksgiving service at St George's Chapel, Windsor Castle earlier on Tuesday.
Lady Gabriella, a godchild of the late Constantine, and her brother, Lord Frederick Windsor, were absent from the memorial.
The Prince of Wales, also a godchild of the former Greek monarch, pulled out of attending at the last minute, but his absence was due to a personal matter and was understood not to be connected to news of Mr Kingston's death.
Earlier this month, Lady Gabriella and Thomas were among the relatives to join Queen Camilla at a star-studded night out to celebrate the work of Shakespeare.
The couple had been set to celebrate their fifth wedding anniversary this May.
Who is Lady Gabriella Kingston?
Prince and Princess Michael of Kent's only daughter was born at the Lindo wing of St Mary's hospital in London on 23 April 1981.
She grew up at Kensington Palace, and she later studied Comparative Literature and Social Anthropology at Brown and Oxford universities.
While she does not carry out royal duties, Lady Gabriella is currently a freelance writer and contributes to an array of publications, including The London Magazine, Conde Nast Traveller, Sustainable First and Cabana magazine.
When did Lady Gabriella begin dating Thomas Kingston?
The pair were reportedly introduced by mutual friends and were first pictured together at Cheltenham Festival in 2015. After dating for a number of years, their engagement was announced by Buckingham Palace in September 2018.
Thomas, who worked as a director at Devonport Capital, proposed to Lady Gabriella the previous month on the Isle of Sark.
The financier reportedly dated the Princess of Wales's sister, Pippa Matthews, for a brief period in 2011.
Lady Gabriella and Thomas Kingston's wedding
Almost exactly a year after Prince Harry and Meghan Markle's nuptials, Lady Gabriella and Thomas were wed at St George's Chapel Windsor on 18 May 2019.
For the beautiful spring ceremony, Lady Gabriella wowed in an embroidered gown by Italian designer Luisa Beccaria and the Kent City of London Tiara – once worn by her grandmother, Princess Marina of Kent.
The bride had several outfit changes throughout the day - she changed out of her embroidered gown and into a new frock for the evening celebration, followed by a dress for when the newlyweds left the reception. She also wore another dress by the same designer for a brunch the following day.
Guests at the wedding included the late Queen Elizabeth II, the late Duke of Edinburgh, Prince Harry, Princess Beatrice and Sarah, Duchess of York.
Lady Gabriella's nieces, Maud and Isabella, who are the daughters of Lord and Lady Frederick Windsor, were given starring roles as flower girls.
A reception took place at Frogmore House in Windsor, where guests tucked into canapes and food bowls. Fiona Cairns, who created Prince William and Kate's wedding cake, also made Lady Gabriella's beautiful tiered cake.