Extracts of intimate letters from Princess Diana to Dodi al-Fayed were read out at an inquest into their deaths in a London court on Friday, and Dodi's father's lawyer said they showed the relationship was serious, not just a holiday fling.

In one letter Diana thanks "Darling Dodi" for a holiday on his yacht, adding "This comes with all the love in the world and as always a million heartfelt thanks for bringing such joy into this chick's life."

In another exchange, dated August 13, 1997 -- a week after the first media reports of their affair and just over two weeks before the couple were killed in a Paris car crash -- Diana sent him some cufflinks which had belonged to her father.

"Darling Dodi, these cufflinks were the very last gift from the man I loved most in the world, my father," her letter said.

"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, Diana."

Dodi's father Mohamed al-Fayed, owner of the Harrods luxury store in London, says Diana and his son were killed by British security services on the orders of Philip, Queen Elizabeth's husband and father of Diana's ex-husband, Prince Charles.

Al-Fayed alleges the killing was ordered because the couple were about to announce their engagement and Diana was pregnant. He claims the royal family did not want the mother of the future king to have a child with his son.

Michael Mansfield, the lawyer representing al-Fayed at the inquest, produced the extracts from the letters as he quizzed the princess's friend and close confidante, Rosa Monckton, about the couple's relationship.

"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," Mansfield asked her.

Monckton replied that Diana tended to speak and write in an extravagant way but agreed the letters were not just written to make someone happy.