Today is Commonwealth Day - a major fixture in the royal calendar that sees members of the Firm come together for a special service at Westminster Abbey each year.
Last year's celebration was cancelled due to the Covid-19 pandemic, but the previous service in 2020 was awash with royals from the Duke and Duchess of Cambridge to Prince Harry and Meghan Markle and, of course, the Queen.
However, this year, the guest list is set to look very different as much has changed in the Royal Family over the past two years.
And on Friday, it was announced that the Queen would not be attending after suffering problems with her mobility.
The 95-year-old monarch is understood to be experiencing increasing discomfort when it comes to getting about.
So who will be at today's service, and who won't be attending? Here we take a look...
Attending
Prince Charles and Camilla
One couple definitely attending this afternoon's event at Westminster Abbey is Prince Charles and his wife Camilla, the Duchess of Cornwall.
After it was revealed that the Queen would not be attending, it was announced that heir to the throne Charles would be representing Her Majesty.
In 2018, it was confirmed that when Charles becomes King, he will also become Head of the Commonwealth after an agreement between Commonwealth leaders at the Commonwealth Heads of Government Meeting in London.
Prince William and Kate Middleton
Another couple definitely attending today's service is Prince William and his wife Kate.
They attended the last Commonwealth Day service in 2020, where much was made of their interaction - or lack of - with Prince Harry and Meghan Markle.
Their appearance today at Westminster Abbey comes just days before they embark on a week-long tour to the Caribbean, where they will visit Belize, Jamaica and the Bahamas.
Princess Alexandra
One of the lesser-known royals attending today is the Queen's cousin Princess Alexandra.
The 85-year-old is a younger cousin of the Queen and was one of her bridesmaids on her wedding day.
The two are thought to have been close companions since childhood with Alexandra regularly supporting the Queen at official engagements.
Speaking on the documentary Princess Alexandra: The Queen's Confidant, royal biographer Hugo Vickers said: "The most successful members of the family are the ones who do not compete with the Queen but who are supportive of her, and she's very much in that category."
Not attending
The Queen
It was announced on Friday that the Queen would not be attending today's Commonwealth Day service.
It is the first time since 2013 that she has missed the event as on that day, she was recovering from a nasty bout of gastroenteritis.
Before that, the Queen had not been absent from a Commonwealth Day observance service for 20 years, the last time being when she had flu in 1993.
The head of state, who has recently recovered from a bout of Covid, hoped to join Prince Charles, Camilla, Kate and William at the Commonwealth event.
The decision is not linked to any illness, but is related to the Queen’s comfort of getting to and from the service.
Prince Harry and Meghan Markle
Since the last Commonwealth Day service in 2020, Prince Harry and Meghan Markle have left their royals roles to carve out new lives in the US.
In fact their last engagement as working royals was the Commonwealth Day service two years ago - where many remarked on the tension between the pair and other members of the Royal Family.
As they are no longer working members of the Royal Family - and now live in California - neither will be attending today's event.
Prince Andrew
Another royal who won't be attending the Commonwealth Day service is Prince Andrew - as he has quit public life and no longer attends royal events.
He also did not attend the event in 2020 as it came just months after his infamous car crash interview on BBC Newsnight, where he spoke at length about his association with the convicted sex offender Jeffrey Epstein.
Earlier this year, he reached an out of court settlement with his accuser Virginia Giuffre in a civil sex claim filed in the US and was stripped of his military affiliations and royal patronages.
Duke and Duchess of Gloucester
Two royals that had been due to attend today's were the Queen's cousin Richard, the Duke of Gloucester and his wife Brigitte, the Duchess of Gloucester.
However, it was announced on Friday that the Duke had tested positive for Covid-19.
He and his wife are therefore isolating and cannot attend the service.
