Princess Diana's last days: The French cleric who forged bond with her mother

For Father Yves, with my thank you's forever, for praying beside my beloved Diana,' reads the handwritten message inside the Christmas card. 

It is decorated with a stained-glass depiction of the Adoration of the Magi and was bought at the Victoria and Albert Museum in South Kensington. The inscription is signed: 'With Love, Frances.'

Confidential papers relating to the death of Princess Diana are held under the 30-year rule at the National Archives in Kew. 

But a touching, and until now private, collection of letters, faxes, cards and cuttings connected to the tragedy lies in a battered blue box file held together by sticky tape in a Catholic presbytery in Paris.

These days, the welfare of the migrants and crack addicts who gather in the nearby Jardins d'Eole in the downtrodden 19th arrondissement are the most pressing concern of the man to whom the letters are addressed. 

But for one night, almost a quarter of a century ago, Father Yves-Marie Clochard-Bossuet's attention was devoted to the soul of the most famous, most glamorous woman in the world. 

And for that he won the lasting gratitude and friendship of Diana's mother, Frances Shand Kydd.

The pair not only became regular correspondents, but dinner companions. 

And what an odd couple they must have presented to the world, alighting from the priest's small hatchback amid the playboy supercars pulled up outside Paris's hottest hotels and restaurants; he in full clerical garb, she in the quintessential evening wear of an elderly but stylish British aristocrat.

Their friendship is one of the few untold stories related to the death of Diana; an unlikely connection between two eccentric people from different backgrounds. 

It offers a new insight into the troubled and enigmatic Shand Kydd, who was in many ways so like her youngest daughter — with whom she had a complex relationship.

Frances Shand Kydd's life appeared gilded but was marred by tragedy and disappointment.

She was born in 1936 at Park House on the royal Sandringham estate. Her father was the 4th Baron Fermoy and a friend to the future King George VI: her mother became lady-in-waiting to the Queen Mother. 

Like her most famous child, Frances was strikingly beautiful and married, at just 18, one of the country's most eligible — and much older — bachelors, John Spencer, Viscount Althorp, 30, at Westminster Abbey. The Queen was among the guests.

They were to have five children. But the death of her firstborn son, John, when he was hours old caused her lasting distress.

Nor was her marriage a success. In 1967, she left her husband for Peter Shand Kydd. The split saw her vilified as a 'bolter' and prompted a bitter custody battle in which Frances's mother Ruth, Lady Fermoy, gave evidence against her. The conflict had a lasting impact on Diana.

The Shand Kydds eventually moved to a farm on the Scottish island of Seil. But this self-imposed exile did not bring happiness. In 1988, Peter left Frances for a younger woman. She remained on Seil and found solace in religion, converting to Catholicism at 58, devoting her life to the Church.

So did Yves-Marie Clochard-Bossuet. But he came to it by a very different path.

As a young man, he had worked on oil platforms in Africa, surfed in California and lived in a hippy commune in New York.

Then he 'got more serious', joining Air France as a commercial attache. He flew the world first class, staying in the best hotels and throwing parties for clients. He had fallen in love and even thought about marriage, but that was forgotten when he experienced a 'realisation', while sheltering from the weather in a church.

His last engagement for the airline was to host a roof-top party at the Cannes Film Festival, at which he recalls talking to the director of the porn film Emmanuelle. Three weeks later, he was living in a monastery off the Riviera. He took holy orders at the age of 42.

He was still new to the calling when, on the weekend of August 30-31, 1997, he was duty chaplain at the Pitie-Salpetriere University Hospital in central Paris.

As the Mail has already described in this landmark series and podcast that re-examines Diana's last days, he was summoned from his bed when Diana was brought critically injured to the hospital after a car crash. 

He kept vigil over her body for ten hours until Prince Charles and Diana's two sisters arrived. He then conducted prayers with the royal party where she lay.

He told the Mail he was 'astonished' by the global reaction to Diana's death. And so horrified by the spotlight he found himself in that he took several weeks' leave in a monastery in Bosnia. He also wrote to Frances Shand Kydd.

'I have an English cousin and it was he who told me that Diana's mother was a Catholic convert with a strong faith. He suggested I should write to her,' he recalls.

'And so I wrote to her a very formal letter giving all the details [of the day of Diana's death]. I wanted to tell her mother the nurses who had taken care of her had done things very well. There was nothing to complain about [even if] it was a hospital room and not in Buckingham Palace. And I told her that I had prayed and had stayed until the arrival of Prince Charles.'

He did not expect a reply, assuming it would be one of a multitude of letters she received: 'But only a few days later I received a touching letter from her. She thanked me, because I was the first to give information directly to her. 

'No one else had communicated with her. Not the management of the hospital, not the doctors, not Buckingham Palace. She was also glad it was a Catholic priest who was there.'

Shand Kydd asked the priest if he would hold a private memorial Mass at the hospital where Diana died, asking him to keep it a secret. 'It was difficult to have a Mass in private without anyone finding out, but anyway, I managed it because I only invited people who were in the same

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