When Peter Phillips and his bride-to-be attended the King's Easter Sunday service at Windsor last weekend, it was Harriet Sperling's formal debut among the rather high profile family she will shortly marry into.

And accompanying the single mother, who works in the NHS, on this no doubt slightly daunting occasion was her only child Georgina, 13 - for whom the very public event must have been, if anything, even more daunting.

What neither Harriet nor Georgina could have known was that while they were nervously meeting their 'new family', their every step was being closely watched - indeed prayed over - by someone from Georgina's 'old family'.

For willing them both on to shine on their Royal debut was a man neither of them have ever met: Georgina's paternal grandfather, Domenico Di Martino.

Mr Di Martino is one of the estimated two million older people in the UK to suffer what is known as 'grandparental estrangement' - having lost contact with his own son some years before he became Harriet's first husband and Georgina's father.

Today, in a candid and moving interview, the first he has ever given, Mr Di Martino tells how he came to miss out on being a part of his granddaughter's life and explains why he blames himself for how his own family became fractured.

The retiree told the Daily Mail: 'I saw Georgina at the Easter service and she's a beautiful young woman.

'It breaks my heart that she's my oldest grandchild - but I don't know her at all.

'She could walk past me and not even know who I am - and that makes me very sad.'

Much has been made of the fact that the Royals will be welcoming their second so-called 'blended family' when Peter and Harriet marry - the groom has two daughters from his first marriage, Savannah, 15, and Isla, 14, whom he shares with his ex-wife, Autumn Kelly.

And the two girls will on June 6 become older step-sisters of Georgina - just as when Princess Beatrice married financier Edoardo Mapelli Mozzi, who already had a young son from a previous relationship, Christopher 'Wolfie' Woolf, before they had daughters Sienna and Athena together.

But the details of how Harriet's first marriage breakdown was foreshadowed - and, according to Mr Di Martino - partly caused by an earlier divorce have never been made public until today.

Mr Di Martino's son and Harriet's ex-husband is fitness instructor Antonio St John Sperling, 44.

Mr Di Martino, 80, has neither seen nor spoken to Antonio for almost 25 years and believes that his son was left with 'deep emotional wounds' that he may have carried into his marriage.

Mr Di Martino explained: 'I left my wife and Antonio's mother Sonia around 25 years ago and he took it really badly.

'When I left his mother, it was hard for him, and he never recovered from that.

'Since then, I've had no contact with him at all. The only news I got about him was from his friends and some family members.

'I knew he got married to Harriet but that only lasted around two years and then he lost his wife and daughter.'

He went on: 'Antonio was angry and broken and I suspect that may have affected his own marriage.

'I have heard that he wasn't happy in the marriage, not because of Harriet but because he wasn't happy in himself.

'I don't think he ever got over the pain of me leaving his mother.'

Mr Di Martino revealed that he was not invited to Antonio and Harriet's marriage, some 16 years ago, and has never met or even spoken on the phone with his former daughter-in-law.

In fact he only learned they were getting married - or later, when Georgina was just two, that they had separated - from third parties.

He said: 'Antonio lost his wife and daughter and that must have left him very sad.

'I don't think he's recovered from that along with me leaving his mum.

'Sadly, Sonia and I splitting meant that he carried a lot of emotional baggage into his marriage, and it clearly was too much for them both. He was very damaged and probably still is.'

Grandparental estrangement is so prevalent that as many as one in seven grandparents are thought to experience it - a number so high it has been described as 'a silent epidemic'.

Mr Di Martino admits that he has closely followed every mention of Georgina in the media since the announcement of her mother's impending marriage - and has also found himself feeling close to the former daughter-in-law he never met.

He said: 'I wish her all the best in the world and I'm very happy that she's going to be a member of the Royal Family.

'I've never met Harriet, but I feel as if I have a connection to her and I'm sure she'll make a wonderful wife for the late Queen's grandson.

'I never want any harm to come to her or my granddaughter even though I'm not even sure that they know of my existence.'

After Mr Di Martino left Sonia, Antonio stopped using his father's surname and took his mother's maiden name of Sperling instead.

Mr Di Martino said: 'That hurt me a lot too. The Di Martino name is more than 1,000 years old and very well known in the part of Italy I'm from. Antonio came from a very good family, but his emotional problems got too much for him.'

The pensioner emigrated to Britain almost 60 years ago from southern Italy and worked as a hairdresser, running his own salon in Cambridgeshire, where he still lives - alone.

He met Sonia in the late 1970s and they married in September 1981 with Antonio arriving soon after.

Recalling Antonio's childhood, he revealed that his son attended the prestigious Kings College School in Cambridge where annual fees are currently close to £30,000 and that he tried to give his son the 'best of everything'.

He said: 'My salon was very successful, and I made a lot of money. I gave my son the best life I possibly could and thought I had done a good job. For the first 20 years he was my son but then he went his own way because he was more loyal to his mother than me.'

Antonio was a prolific rugby player and represented his county and played for professional club Northampton's under 18 and 21 team. He was on the verge of breaking into the first team before a knee injury forced him to give up the game.

Antonio then qualified as professional fitness instructor and also set up his own gym in the Cambridgeshire area.

Sonia died following a short illness in 2017 at the age of 65 with Mr Di Martino admitting that he did not even attend her funeral.

They also have another daughter who lives in London and is two years younger than Antonio, but Mr Di Martino revealed that he only has intermittent contact with her.

Mr Di Martino said that as he looks back on his life, he now regrets leaving Sonia because of the impact it had on Antonio and his marriage to Harriet.

He said: 'I loved my wife very much, but we split; it happened to a lot of people at the time. That was a mistake which I now regret. Who knows, if it hadn't happened, Antonio may still have been happily married to Harriet.'

Even though they had already been estranged for years when Antonio and Harriet became engaged, he wasn't surprised.

He said: 'Antonio is 6 feet 3 inches and a very good-looking man. Women were always interested in him and he had no problem meeting them.

'He dated a lot of women in his younger years. He had classical Italian features and women were falling at his feet.'

Harriet has previously spoken frankly about her struggles as a single mother following the breakdown of her marriage.

In a first-person essay for Women Alive, she revealed how she and Georgina survived 'against the odds' as they 'journeyed 10 years with only each other' while she juggled parenting with working on the NHS frontline.

She also confessed that it 'has often felt hard to imagine' anyone else coming into their lives in the piece that was published in March 2024.

Soon after, however, Harriet met Peter when their paths crossed at a sporting event, and he is said to have quickly become besotted with her.

Harriet and Peter are set to marry at All Saints Church in Kemble, Cirencester, in a private ceremony.

Peter is the eldest grandchild of the late Queen, son of Princess Anne and her first husband Mark Phillips, and is 19th in the line of succession to the throne.