Mid-morning on 6 September 1997 and I am sitting in a beach-side hotel in Alghero, Sardinia, watching T.V. with the hotel owner. This middle-aged Italian lady occasionally dabs a handkerchief to her face, quietly sobbing. Outside crystal waters lap onto golden sands in 30-degree heat, and holidaymakers laze in the gentle Mediterranean waves, but the two of us sit glued to the T.V. Practised cynic and seasoned realist, now I find myself holding back the tears, overcome by emotion. What is happening?

What was happening was Princess Diana's funeral, and I found myself overwhelmed just like the million people lining the funeral procession route. And I wasn't even there! So the question I have often asked myself since is: how real was that emotion?

Certainly there have been many examples of mass outpourings of grief but the British reaction to the death of "Princess Di" was exceptional. Millions of supposedly reserved Brits took to the streets, massing outside Buckingham Palace, laying flowers, demanding action. Even the Queen temporarily lost control, rushing back from Scotland and lowering the Royal flag against all historical protocol (and when you are a monarch, protocol is everything).

The death of Eva Peron (Evita) was a case in point. This so-called hero of the people, of the working classes, of the "descamisados" (shirtless ones), was mourned by millions when she died during the evening of 26 July 1952. At 8:25 p.m., the moment of her death, movie theatres stopped playing, customers were shown out of restaurants in the middle of their meal, radio broadcasts were interrupted to break the news, and Argentina went into a deep state of collective shock. Millions took to the streets -  within a day all flower shops in Buenos Aires had run out of stock.

Hers was a very public death with tragic overtones - just like Alexander the Great and Jesus Christ, Evita lived to just 33. There were some, of course, that claimed that the reaction was, at least in part, orchestrated by the Peronist regime, or that the myth had been built up by Peron herself. But whatever the cause, the grief, the weeping and the chanting actually happened, and those emotions, however induced, were real.

The current death for our times is of course that of Michael Jackson: a tragedy of Shakespearean proportions. This was a star on the verge of a comeback, overcoming his demons and returning from the brink of disaster. Then a sudden and unexpected nemesis, all under the glare of an incessant media spotlight. If Kennedy's was death-by-motorcade then Jackson's could only have been death-by-tabloid.

Then, the reaction. Fans who, like me, last bought his records in 1983 suddenly reappear to proclaim his genius. Websites are flooded, news channels roll 24/7, a ticket lottery is held for the ultimate media funeral. Rapacious reporters lurk, desperately feeding the media monster and searching for any news, however tiny, of drugs, scandals, custody battles, family feuds. A collective sadness hangs in the air, the shock of realising that this was a human being after all. Was it, in the final analysis, all our fault?

And then, in the space of a few days, it's over. The media caravan moves on to the next story, leaving barely a footprint in the sand. The tragic icon is consigned to the history books, and we are left to wonder what we really feel.

The death of a celebrity, the speech of a war leader, love for the king or assassination of a hero - none of us are immune to mass emotions - these are surely hard-wired into the human psyche. Only the context, culture and characters differ. These emotions are very powerful, and we actively seek them, perhaps unconsciously. But they appear in an instant, and in an instant they vanish, as if they had never existed. They are impossible to label, and yet they are very, very real.

Crowd emotions will always be with us, and their importance should never be underestimated. Ask Adolf Hitler.