King Charles became the first British monarch in some four centuries to attend a Roman Catholic funeral on Tuesday when he joined members of his family for a requiem mass for the Duchess of Kent, the wife of a cousin of the late Queen Elizabeth.

The duchess, Katharine Worsley, who joined the royal family when she married Prince Edward, the Duke of Kent, in 1961, died on September 4, aged 92.

Best remembered for her close association with the Wimbledon tennis tournament, where from 1969 she helped to hand out the trophies, she was also known for converting to Roman Catholicism in 1994, becoming the first British royal to do so since King Charles II, who turned to the faith on his deathbed in 1685.

CHARLES BREAKS WITH ROYAL TRADITION

Thus it was a break in tradition for Charles, the Supreme Governor of the Protestant Church of England, to attend the funeral for the duchess at London's Westminster Cathedral, where the service was conducted by Cardinal Vincent Nichols, the leader of Catholics in England and Wales.

Also present were the king's son and heir Prince William and his wife Kate, although Charles' wife Queen Camilla had to pull out as she was recovering from acute sinusitis.

"The funeral will be of great historical significance," Catherine Pepinster, former editor of the Catholic weekly review, The Tablet, told the Sunday Times. "This is a huge step forward in ecumenical relations."

Following the funeral, the duchess' coffin was to be taken to a burial ground at Frogmore on the royal estate surrounding Windsor Castle, which is preparing to host U.S. President Donald Trump for a state visit from Wednesday.

Charles has for many years stated that he wishes to protect all faiths, and he and his wife Camilla were among the last official visitors to see Pope Francis before his death in April.

Pope Leo XIV said he was saddened to learn of the duchess' death in a message to the king which was read out at the service.