Princess Beatrice will only be able to have two guests at her wedding if the coronavirus crisis continues.
The Church of England has said the number of people attending church weddings during the outbreak should be limited to the legal minimum of five – the priest, the bride and groom and two witnesses.
The Queen's granddaughter and her fiance Edoardo Mapelli Mozzi have already cancelled their reception, which was due to take place in the gardens of Buckingham Palace.
Beatrice and millionaire property tycoon Edo said on Wednesday that they still plan to wed on May 29, but were looking at whether a private marriage with a small group of family and friends would be feasible.
Beabea – wow! I'm so happy for you my dearest big sissy and dear Edo. It's been a long time coming and you two are meant to be. 📷 by me!! "We are extremely happy to be able to share the news of our recent engagement. We are both so excited to be embarking on this life adventure together and can't wait to actually be married. We share so many similar interests and values and we know that this will stand us in great stead for the years ahead, full of love and happiness"
A post shared by Princess Eugenie (@princesseugenie) on Sep 26, 2019 at 3:10am PDT
But the new Church of England rules means they will only be able have two family members or friends if the pandemic continues.
This means Beatrice could have her parents but not her sister Princess Eugenie as well.
Couples are being advised to "stream" their ceremony to absent friends and family.
Beatrice, daughter of the Duke of York and Sarah, Duchess of York, is set to walk down the aisle in the Chapel Royal of St James's Palace in London.
The princess, 31, was overjoyed after becoming engaged on a weekend trip to Italy last September, and the couple said they could not wait to be married.
Her forthcoming nuptials have already been overshadowed by the scandal that has engulfed her father Andrew.
The duke retired from public royal duties in November after his disastrous Newsnight interview about his friendship with convicted sex offender Jeffrey Epstein.
Andrew has strenuously denied claims from Virginia Giuffre that he slept with her when she was 17 after she was trafficked by Epstein.
The duke is facing calls to talk to the FBI and US prosecutors, but has previously been accused of having "completely shut the door" on any co-operation.
As the granddaughter of a monarch, Beatrice would have been expected to wed in front of 800 guests in St George's Chapel, Windsor Castle, just like her sister Princess Eugenie, whose ceremony was televised and was followed by a carriage ride through the town.
But, amid the controversy over her father, the princess opted for the more intimate, low-key option of the Chapel Royal and was due to invite 150 guests.
Prior to the coronavirus outbreak, Beatrice would have wanted her grandparents the Queen and the Duke of Edinburgh to be with her on her wedding day.
The Queen was to host the private reception in the grounds of her London residence.
But the Government has called on all people in the UK, particularly the over-70s, to avoid all non-essential contact and travel as part of unprecedented peacetime measures aimed at controlling the spread of Covid-19.
The Queen, 93, and the 98-year-old Duke of Edinburgh are at Windsor Castle, where they are socially distancing themselves.
Mr Mapelli Mozzi has dual British and Italian citizenship.
Italy – the worst-hit European country – is in lockdown.