Mary Dejevsky: Why does Mohamed Al Fayed get such stick?

How the great and good of the British establishment must be rejoicing – discreetly sheltered by their castle walls and stucco facades. They finally granted Mohamed Al Fayed his yearned-for day in court, and now the whole Diana conspiracy has evaporated in the steam of his own overheated rhetoric. That's what we call fair play, old chaps, fair play.

But it is not fair play at all, is it? All right, so Mr Al Fayed appears to have been treated with due deference inside the court, as the bereaved father he will remain for the rest of his days. As a key witness and man of material substance, he might have hoped for gentler handling, but even the most hostile questions never went beyond the pale. Dodi's father was allowed his dignity. There is still such a thing as courtroom etiquette, and far be it from the establishment to breach it.

Outside the court, it was another matter. The media coverage was merciless. Front pages hurled invective. Yet most merely reproduced Mr Al Fayed's own colourful expressions. There was no need to embellish, still less ridicule. The owner of Harrods had done it all himself.

So much for the headlines. The accompanying reports dripped with innuendo. There was race – who was this man, it was implied, to speak of our Royal Family as "Draculas" who would never accept his son? Silent answer: an Arab with the excitability that belongs to that alien part of the world. And there was class: in all the references to the billions Al Fayed spent lurked disdain for a shopkeeper made good. Oh, and he wasn't quite dressed for the occasion; the wrong sort of check, you know. At once condescending and contemptuous, the reports let us know that this Al Fayed character, whoever he was, was definitely, positively, not "one of us".

Could such negative – no, insulting – coverage have been predicted? Of course. It was no more surprising than The Sun headline, "45 Minutes from Doom" that followed publication of the dossier stating the time within which Saddam Hussein could deploy his non-existent weapons. Once you know how the relevant sections of the popular press work, you can play them like the proverbial violin.

In giving Mohamed Al Fayed his day in court, the establishment took the most negligible of risks. Short of failing to turn up or answering in curt monosyllables, there was nothing Mr Al Fayed could do to escape the trap. Too emotional? Too un-British? Too... er, common? You almost wonder why, if it was going to be so easy to damn his credibility with his own words, he wasn't invited to the witness box a decade earlier.

Those of us who still suspect that more lies behind Diana's death than an irresponsible French driver, were dismissed as fantasists, who now had to believe what the establishment had told them. Because Al Fayed was emotional and hyperbolic, every aspect of his story was judged unworthy of consideration; he was speaking cock and bull.

Yet the one does not follow from the other. How many times do you have to say this: here is a father, bereft of his elder son. You can argue, if you like, that he has money and interests sufficient to absorb his sorrows – unlike fond fathers of lesser means. You can criticise his son's lifestyle: to put no finer point on it, Dodi was a playboy; one hopes Diana knew the life she was getting herself into. You may have views on Mohamed Al Fayed's character or his merits as a businessman.

That he may not have presented his case in the most convincing way for an audience more attuned to understatement, however, does not mean that his belief in a conspiracy is discredited. There are old questions that remain unanswered: that white Fiat Uno; the French paparazzo found later with his throat cut; the contradictory accounts of the chauffeur's drinking habits; Diana's fears that she would die in an arranged car accident; and the presence of an MI6 team in Paris on the fateful weekend.

And there are new questions that have been raised by this inquest: not least why witnesses at the scene who volunteered their accounts were not properly interviewed at the time. It is also curious that the Metropolitan Police failed to come clean about Diana's written fears for her life after she died. You might also add the claim that the secret services experimented with dazzling lights for the purpose of causing road accidents. But that came from a supposedly discredited former agent, so it can't possibly be true – can it?

As the Diana inquest lumbers on, Mohamed Al Fayed's testimony is being held up as proof that the whole exercise was ill-conceived and futile. It is a classic case of allowing the messenger to obscure the message. I wonder in whose interests that might be?