Details of letters written by Princess Diana to Dodi Al Fayed have been revealed at the inquest into the couple's deaths.
Princess Diana and Dodi Al Fayed died in a car crash in August 1997
The princess wrote "with all the love in the world" and of him "bringing such joy" into her life in August 1997.
The letters were produced during the cross-examination of Diana's close friend, Rosa Monckton.
In one letter Diana described a gift to Mr Al Fayed - cufflinks which belonged to her father.
On 13 August 1997 the princess wrote about the gift: "Darling Dodi, these cufflinks were the very last gift that I received from the man I loved most in the world, my father.
"They are given to you as I know how much joy it would give him to know they were in such safe and special hands. Fondest love, from Diana."
In a letter from Kensington Palace dated 6 August 1997, Diana thanked Mr Al Fayed for a six-day holiday on his yacht.
She wrote: "This comes with all the love in the world and as always a million heart-felt thanks at bringing such joy into this particular chick's life."
Michael Mansfield QC, who is representing Mr Al Fayed's father Mohamed, produced the letters in an attempt to demonstrate the relationship between Diana and Mr Al Fayed was a serious one.
BBC royal correspondent Nicholas Witchell said over the coming days the inquest would test the conspiracy theories to discover whether there was a motive for anyone to commit murder.
On Thursday Ms Monckton played down the couple's relationship, saying they were not about to get married and that Diana was not pregnant when she died.
During cross-examination by Mr Mansfield, Ms Monckton broke down in tears.
Diana, Dodi Al Fayed and driver Henri Paul died in a car crash in a Paris road tunnel in August 1997.
Mohamed Al Fayed, the owner of Harrods, has claimed there was a plot involving the Duke of Edinburgh to murder Diana and his son.
Mr Mansfield asked Ms Monckton: "She was treating this relationship with Dodi as a serious matter, wasn't she? It doesn't suggest it was little more than a fling after a couple of days."
She replied: "She tended to speak and write in an extravagant way."
But Ms Monckton agreed the letters were not just written to make someone happy: "It was clearly more than that."
Ms Monckton denied Diana had finished a relationship with heart surgeon Hasnat Khan because she was in love with Mr Al Fayed.
The questioning of friend Rosa Monckton was "close to the line"
She was asked if Diana had misled her because she was concerned about Ms Monckton's "hostility and animosity" towards Mr Al Fayed.
Ms Monckton said: "She was not misleading me. We talked about it a lot."
She added: "She told me Hasnat would never have her back once the photographs of her with Dodi had appeared and she was very upset about it."
Ms Monckton tearfully described Diana as a "very true and close friend" but said that did not stop the princess from not telling her everything.
There was a short adjournment to the hearing, after which coroner Lord Justice Scott Baker told Mr Mansfield he had come "fairly close to the line" in his questioning.
Ms Monckton said Diana regretted her television interview with Martin Bashir in which she described Prince Charles' side as the enemy.
Model Kelly Fisher, a former girlfriend of Dodi Al Fayed, told the inquest she met him in the summer of 1996.
She said she had "no doubt" a ring she was given by Mr Al Fayed in February 1997 was because they were engaged to be married.
Model Kelly Fisher was Dodi Al Fayed's girlfriend before Diana
Ms Fisher said Mr Al Fayed told her Diana had accepted an invitation for a holiday with the Al Fayed family in Saint-Tropez from 11 to 20 July, 1997.
Ms Fisher said she was under the impression she was going to Saint-Tropez with him but he lied about having to go to London instead.
On 6 August she was called by a friend who told her about the publication of a photograph of Diana and Mr Al Fayed kissing.
Ms Fisher said when she spoke to Mr Al Fayed on the phone she taped the conversation, which she would provide to the court.
Cross-examined by Mr Mansfield, Ms Fisher said she never wanted to talk about the tape but was tired of people saying she was a liar.