Harry had been due to attend the event at Kensington Palace, and, his absence will undoubtedly be perceived as a snub to the Royal family.
The party honoring the late Princess of Hearts had originally been planned for the 1st of July, when the brothers unveiled a statue of Diana, Princess of Wales, on what would have been her 60th birthday.
37-year-old Prince Harry flew back to attend the unveiling, yet he was present without his wife Meghan Markle, who had given birth to the couple's second child three days after the reveal of the monument. Lilibet Diana was born on the 4th of June.
Due to COVID-19 pandemic restrictions, the plans had to be somewhat changed, with just the Princes, their uncle Earl Spencer and aunts Lady Sarah McCorquodale and Lady Jane Fellowes present at the ceremony. Prince Harry is expected to attend the rescheduled party for 100 guests, which will, presumably, include Sir Elton John, on the 19th of October, though, it is not yet clear if this time Meghan would accompany her husband
Lilibet Diana still has to meet all other Royal Family members face to face. Her brother Archie, who is currently 2 years old and was christened at Windsor in July 2019, has not been in the UK for more than a year.
After attending the statue's unveiling ceremony, Prince Harry made an announcement that he had started to write his memoirs. The book is expected to be released next year, when the Queen will celebrate her Platinum Jubilee, marking 70 years on the throne.
According to some insider information presented to the press:“The delayed party had initially been planned for September, but it was put back again as they had to check diaries.”
This week a spokeswoman for the Royal Family reportedly confirmed that the Sussexes would not be coming to the ceremony, even though such a gesture might be perceived as a sign of the intensifying clash between the princes. Nevertheless, Kensington Palace did not give any comments to the press regarding the discussed matter.