Earl Spencer has recalled the moment Princess Anne allegedly made him 'feel small' at a Buckingham Palace dinner two days before his sister Princess Diana's wedding.
The earl said he was sat next to the Princess Royal at a formal event to celebrate his sister's marriage to Prince Charles on July 27, 1981, when he was aged just 17.
Anne's daughter Zara Phillips had been christened earlier that day at Windsor Castle, and the teenaged Spencer attempted to start a conversation on the topic.
While he was expecting a joyful response, he claims Anne instead looked at him 'witheringly' and asked: 'Tell me, how's a christening supposed to go?'
He explained how he immediately 'turned red and looked at my plate, unable to conjure up a reply' – given he was '17 and clueless about dinner party small talk'.
The earl then looked across and saw his brother-in-law Neil McCorquodale having a much happier conversation with the Crown Princess of Japan about 'rice cultivation'.
The claim about Anne – to which she has not responded – is the latest to emerge from the earl's new book 'Swan Song: Diana, My Sister', which has sparked a war of words with Buckingham Palace.
In the book, which was serialised in the Daily Mail last month, the earl writes: 'I was told that I was to be seated on Princess Anne's table at dinner and thought that I must have some conversation to present her with, should she talk to me.'
Earl Spencer's book about Princess Diana has sparked a war of words with Buckingham Palace
The earl was sat next to Princess Anne at the dinner in 1981. She is pictured in York last week
Princess Anne holds her baby daughter Zara Phillips at Windsor Castle on July 27, 1981
Princess Anne (left) and Princess Margaret on July 29, 1981, after Charles and Diana's wedding
'It transpired, to my alarm, that I was actually placed next to Anne, and when she turned my way, I asked, "And how did your daughter's christening go today, Ma'am?" I expected her to run away with the happy topic of her baby Zara's baptism.
'But instead she stopped, looked at me witheringly, and asked, "Tell me, how's a christening supposed to go?" And I, being 17 and clueless about dinner party small talk, turned red and looked at my plate, unable to conjure up a reply.
'Across the room, my brother-in-law Neil, whose family were arable farmers in Lincolnshire, found less fallow ground. Placed next to the Crown Princess of Japan, he had an easy conversation about rice cultivation.
'It was the luck of the draw that night, whether you were placed next to a royal who was happy to make you feel small, or one who had the grace and manners to look for common ground, wherever it might be found.'
The earl's book has made headlines around the world for its string of allegations against Charles, including that he said 'we'll forget her soon enough' about Diana.
The comment was allegedly made during an argument in 1997 over whether Princes William and Harry should walk behind their mother's coffin in her funeral procession.
The memoir, released on September 22, also claims that Charles 'sounded giddily elated – like a lottery winner' when he spoke to the earl after Diana's death.
In a strongly worded response last month, Buckingham Palace said the King was 'mindful that the pain of fraternal grief can cloud reason, affect judgement and colour memory in ways others do not recognise, even many years after such a loss'.
The Palace today declined to comment about the claim relating to Anne.