Princess Charlene did not accompany her husband, Prince Albert of Monaco, at the memorial service which is being held in honour of Prince Philip on Tuesday.
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The 44-year-old, who continues to recover from her recent health battle, recently returned to Monaco where she was reunited with her family.
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Earlier this month, a statement issued by the Prince's Palace of Monaco confirmed that the mother-of-two is back in Monaco and will continue her "convalescence in the Principality with her husband and her children by her side."
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The royal spent much of 2021 in South Africa following an ENT infection that she picked up during a visit. But she had since been receiving care in a Swiss clinic since November.
While Prince Albert confirmed that she was dealing with "exhaustion, both emotional and physical", Princess Charlene collapsed on 1 September due to complications following one of several surgeries for a severe and ongoing ear, nose and throat (ENT) infection.
Prince Albert of Monaco seen at Westminster Abbey on Tuesday
She was rushed to Netcare Alberlito Hospital, and the Palace released the following statement to People: "On the night of September 1, Her Serene Highness Princess Charlene of Monaco was taken to hospital after becoming ill due to complications from a serious ENT infection. Her Highness is being closely followed by her medical team, who say her condition is reassuring."
Meanwhile, around 30 foreign royals, including her husband Albert, was at the ceremony for Prince Philip. Other royals included Denmark's Queen Margrethe, King Harald and Queen Sonja of Norway, and Spain's King Felipe and Queen Letizia.
Princess Charlene remained in Monoco on Tuesday
The Duke's wider family and friends were also there, along with 500 representatives from his patronages and charities. The service is expected to pay tribute to the Duke of Edinburgh's dedication to "family, nation and Commonwealth", his contribution to public life and his steadfast support to his charities.
It also incorporated some elements planned for the late royal's funeral, which were unable to go ahead due to COVID-19 restrictions in place at the time.
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