Queen Margrethe's sister Anne-Marie of Greece, 75, had to pull out of the upcoming Danish sovereign's Jubilee events in the wake of health concerns for her husband. The former Queen of Greece was due to attend a series of engagements in Denmark later this week, including a visit to the grave of her parents.

       But she can no longer travel home after her husband, the deposed monarch of Greece Constantine II, 83, was admitted to hospital with COVID-19.

       Constantine, who was King between 1964 and 1973, was admitted to hospital on January 8 and is said to be in good health.

       The royal, who is fully vaccinated against the virus, had already been to hospital last month, after he was found to have had a stroke.

       Anne-Marie is the youngest daughter of Denmark's late King Frederick IX and Queen Ingrid and sister of Queen Margrethe and Princess Benedikte.

       Among the events the sisters were to carry out together, there was a gathering at Roskilde Cathedral on January 14 for a poignant wreath-laying ceremony at the grave of their parents.

       Queen Margrethe, 81, will still be in the company of Princess Benedikte during the emotional engagement.

       January 14 marks the beginning of Queen Margrethe II's Golden Jubilee, as the royal acceded to the throne on that day 50 years ago in the wake of her father's death.

       Jubilee celebrations are set to be kept low-key on Friday due to the ongoing pandemic.

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       The day of engagements will start at 9.30am, when the Queen and her son and heir Crown Prince Frederik will welcome the Prime Minister at Christiansborg Castle.

       Half an hour later, the Queen, Frederik and his wife Princess Mary, Margrethe's second son Prince Joachim and his wife Marie and the monarch's sister will take part in the celebrations at the Danish Folketing.

       The wreath at Roskilde Cathedral will be laid at 12pm.

       Members of the public will be barred from gathering in the Yellow Palace at Amalienborg amid fear of Covid infections rising - but well-wishers will be given the chance to send their congratulatory messages for the sovereign in a special section of the Danish royal website.

       The main celebrations for the Jubilee, however, have been postponed to September, with the hope the country can gather to mark the event without fearing COVID-19.

       Among the planned events not taking place on September 10 and 11 there are “celebrations at Copenhagen City Hall, a gala performance at the Royal Theatre’s Old Stage, festive service in Copenhagen Cathedral and gala dinner at Christiansborg Castle”, according to the royal court's press release.

       Over the past months, Covid hit directly senior members of the Danish Royal Family.

       In December, Crown Princess Mary self-isolated at the royal palace in Amalienborg following a positive test result.

       Her elder son Prince Christian had contracted COVID-19 one year prior, following an outbreak at his school.

       Other Scandinavian royals have also been affected by coronavirus.

       Sweden's King King Carl XVI Gustaf and his wife Queen Silvia discovered to have contracted the virus last week.

       A few days later, it was announced their firstborn Crown Princess Victoria and her husband Crown Prince Daniel had tested positive for the virus for the second time in months.

       Victoria's brother Prince Carl Philip also caught the virus in early 2021, alongside his wife Princess Sofia.