Buckingham Palace said on Tuesday that Queen Camilla is recovering from acute sinusitis.
Camilla, 78, had been due to join the King and other members of the Royal Family at the funeral at Westminster Cathedral this afternoon.
The withdrawal raises questions over her attendance for US president Donald Trump‘s state visit, which begins at Windsor on Wednesday.
The visit is being hosted by King Charles.
But the Queen is hopeful she will recover in time to attend all royal elements of the President’s trip, which includes a lavish state banquet.
A Buckingham Palace spokesperson said: “With great regret, Her Majesty The Queen has withdrawn from attendance at this afternoon’s Requiem Mass for The Duchess of Kent as she is recovering from acute sinusitis.
The Duke of Kent has been informed and is said to fully understand the decision, wishing her a speedy recovery.
The Queen had travelled down from Scotland this morning and is currently travelling to Windsor, where she will rest.
“Her thoughts and prayers will be with The Duke of Kent and all the family.”
The requiem mass, which is a Catholic funeral, is the first to be held for a member of the monarchy in modern British history.
