Queen Elizabeth II on Monday called on the Commonwealth to show unity in troubled times, as she sat out a major event for the organisation after a period of fragile health.
The event with some 1,500 guests at Westminster Abbey in central London had been due to be the 95-year-old monarch's first large-scale public engagement in nearly six months.
But she withdrew on Friday, raising questions about the extent of her participation in future events to mark her record-breaking 70th year on the throne.
British media said palace officials had concerns for her comfort travelling to and from the service, and its duration. The queen turns 96 next month.
She has previously been seen with a walking stick and pulled out of one event last November with a bad back. She has also been overheard complaining about mobility problems.
The Sun newspaper on Saturday said she had been unable to walk her beloved corgis for the last six months while the Daily Mail said she had ruled out using a wheelchair at the service.
The next major event she is due at is the memorial service for her late husband, Prince Philip, who died last April aged 99 and whose funeral was held under Covid restrictions.
Despite her absence on Monday, the queen sent a message to representatives of the 54-nation grouping of mainly former British colonies that she heads.
She notably renewed her pledge of lifelong service to the organisation that she made as a young princess back in 1947, calling it the "family of nations".
Its role -- as "a place to come together to pursue common goals and the common good, providing everyone with the opportunity to serve and benefit" -- was more important than ever in the world, she said.
"In these testing times, it is my hope that you can draw strength and inspiration from what we share, as we work together towards a healthy, sustainable and prosperous future for all," she added.
Charles taking over
Elizabeth's eldest son, Prince Charles, 73, will take over as head of the Commonwealth when he becomes king, after a lifetime as heir apparent.
He represented her on Monday with his second wife, Camilla, and his eldest son from his first marriage to Diana, Princess of Wales, Prince William, and his wife, Catherine.
He and Camilla will likewise be in attendance in Rwanda in June for the Commonwealth Heads of Government meeting, which has been postponed twice because of the pandemic.
Charles is also expected at the Commonwealth Games which are due to take place in Birmingham, central England, in July and August.
Later this week, William and Catherine head to Belize, The Bahamas and Jamaica, officially as part of the Platinum Jubilee celebrations.
But with Barbados having last year abandoned the queen as head of state, it will also be seen as an attempt to dampen wider republican sentiment in the Caribbean.
The queen is head of state in the United Kingdom and also 14 other Commonwealth countries or realms.
The Commonwealth Day service is one of the most important events on the royal calendar, and the queen's absence is the first time she has missed it since 2013.
That year she was recovering from a bout of gastroenteritis. Before that, she missed a service in 1993 as she had flu.
Royal officials gave no reason for her withdrawal this time but she has recently had what was described as a "mild" bout of Covid.
She was forced to slow down in October last year after an unscheduled overnight stay in hospital, which has seen her pull out of a series of public engagements.
Buckingham Palace said she would "continue with other planned engagements, including in-person audiences, in the week ahead".