Those marking their 60th, 65th or 70th wedding anniversaries can request to have a note of congratulations from the monarch. However, many of these are expected to arrive late this year as the global pandemic hits the royal bureaucracy.
In a statement the Palace warned letters could be delayed by a “number of weeks” adding it is “sorry for the disappointment”.
It explained: “Please note that due to operating restrictions caused by COVID-19 measures, our capacity to deal with all message applications is currently reduced and our ability to send messages is limited.
“Wedding anniversary message applications are currently delayed by a number of weeks, applications submitted online and by post since April are being processed as quickly as possible but are severely delayed.”
Members of the public can still apply to have milestone wedding anniversaries marked by the Queen, but there is no guarantee her messages will arrive in time.
This will not impact those expecting letters from the monarch to mark their 100th birthday.
In 2019 the Queen send out more than 36,000 messages of congratulations for wedding anniversaries.
Three years previously she dispatched 29,339 notes for 60th anniversaries, 3,221 for 65th anniversaries and 1,407 for 70th anniversaries.
The Queen and Prince Philip, who wed in 1947, have been married for a total of 73 years.
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Currently the monarch is at her Balmoral estate, in Scotland, where she traditionally spends summers.
Shortly before the coronavirus lockdown began the Queen moved to Windsor Castle to self-isolate.
She is expected to return there later this year amidst fears of a second COVID-19 wave.
Prince Charles did catch coronavirus back in March but only suffered mild symptoms and has since made a full recovery.
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In April the Queen delivered a powerful address to the nation as the battle against COVID-19 was underway.
She said: “While we have faced challenges before, this one is different.
“This time we join with all nations across the globe in a common endeavour, using the great advances of science and our instinctive compassion to heal.
“We will succeed – and that success will belong to every one of us.
“We should take comfort that while we may have more still to endure, better days will return: we will be with our friends again; we will be with our families again; we will meet again.”
This comes after the Duke and Duchess of Sussex announced they were stepping down from royal duties back in January.
After a brief stay in Canada the couple moved to Los Angeles shortly before the coronavirus lockdown came into effect.
Meghan and Harry recently moved to a new home in a town to the north of LA.
During the lockdown both the Duke and Duchess were spotted delivering supplies to vulnerable residents in the city.
Last month ‘Finding Freedom’, a provocative book about their exit from royal duty by Carolyn Durand and Omid Scobie, was published.