The court was on a treasure hunt from the start. The prize was nothing less than the "crown jewels". That's what the private letters between Princess Diana and the Duke of Edinburgh have been dubbed.
Who Diana was with was not Prince Philip's problem, his aide says
Some have suggested the letters, written between June and September 1992 when the princess's marriage was in difficulty, contain evidence of hostility between the two correspondents.
There was no immediate hint of that in the snippets that were revealed by the duke's private secretary, Brigadier Sir Miles Hunt-Davis.
The former soldier stood to attention in the witness box. A distinctive man with a shock of white hair and a navy blue suit, he was effectively the bearer of the envelopes. He has been the duke's private secretary since 1993, his most senior aide.
The coroner, Lord Justice Scott Baker, revealed that he had read the letters and confirmed their sensitive nature. Therefore the court would be shown only the beginning and end of each.
Prince Philip initiated the exchange on 18 June 1992. Princess Diana's reply was projected onto screens.
She began: "Dearest Pa... I was so pleased to receive your letter...." It ended: "With fondest love, Diana."
Those seeking signs of discord may have been cheered that by the time of the second letter, the duke was no longer "Dearest Pa" but merely "Dear Pa". But by 12 July maximum affection had been restored.
Michael Mansfield QC, representing Mohammed Al Fayed, needed to show that the duke wanted Diana dead. He questioned whether these were the only letters in existence.
The brigadier seemed unsure, probably ruling him out of a future career with the Post Office. But by the end of his evidence session it seemed the chances of further letters being delivered were minimal.
In fact, the brigadier had a difficult time being cross-examined. He never quite got to the stage of drawing out the white handkerchief from his upper pocket to wave in surrender.
Diana 'not relevant'
But on numerous occasions he was forced to admit memory lapses or the failure to discuss pressing issues with the duke at all.
Brig Hunt-Davis's main defence was that, once Diana lost her title, she ceased being a member of the royal family and they no longer had to worry about her.
Rosa Monckton was a close friend of Princess Diana.
He said: "Mr Mansfield, I think what you have failed to accept is that actually, once the divorce had happened, what Princess Diana did was not relevant to the mainstream of the royal family."
Rosa Monckton, on the other hand, was far more interested in communicating with Princess Diana.
She gave evidence in the afternoon and brought a completely different style.
At times her voice and manner were spookily reminiscent of her former close friend.
Ms Monckton provided the most personal evidence for the inquiry. She had her first proper meeting with Diana in February 1992 and became one of her closest confidantes.
Ms Monckton said that when Prince Philip first wrote to the princess, Diana was deeply upset and turned to her.
But she told the court that Diana was emotional and she was able to convince her that the duke was acting in good faith.
To the surprise of many, she admitted to actually helping draft the replies which Diana then put into her own handwriting.
"She said, 'Can I come and see you because I have received a letter and it has made me very upset?'" So she came round to our flat in Cambridge Street and we looked at it together and I was able to calm her down and point out that actually this was an offer of help...."
She was certain that Princess Diana was not in love with Dodi Al Fayed, reminding the court that she had only been seeing him for six weeks.
Her real love, according to Ms Monckton, was Hasnat Khan, a prominent heart surgeon who had called off their relationship.
She had intimate knowledge that Diana was not pregnant and was equally certain that she had no intention of getting engaged to Dodi.
Michael Mansfield's job was to focus as much doubt on the closeness of the relationship as possible. He set about the task with relish.
Ms Monckton was forced to concede that Diana kept her friends separate and she may not have been told everything. At times her advice was so unwelcome that it resulted in "radio silence" whereby Diana would not be in touch for two months.
One of these breakdowns occurred when she advised Diana to steer clear of the Fayeds, advice that was roundly rejected.
As the questioning continued, Ms Monckton grew more hesitant and unsure. She strongly rejected accusations that she had betrayed Diana's trust by speaking to the Sunday Telegraph.
She said she had only told the newspaper that the duke's letters to the princess were supportive, correcting misrepresentation elsewhere.
The man at the centre of the arguments was not in court. The Duke of Edinburgh has no intention of being questioned in court, even though his aide was forced to admit there were some questions only he could answer.
But probably everyone agreed with one amusing sentiment expressed by Prince Philip in a letter to Princess Diana: "I will always do my utmost to help you and Charles to the best of my ability, but I am quite ready to concede that I have no talents as a marriage counsellor!"