LONDON // For an older generation, the cliche had been: "What were you doing when you heard John F Kennedy had been shot?" Now, it is indelibly imprinted on people's minds what they were doing when they heard about 9/11.
For me, it was a phone call from the foreign editor of The Daily Telegraph as I was coming to the end of a leisurely pub lunch in rolling English countryside with a police contact briefing me on the background to an upcoming murder trial.
"Get to Heathrow right now," was the order. "An airliner has just crashed into one of the Twin Towers."
Initially, it simply seemed like a dreadful accident. But, as I listened to the BBC coverage on my car radio, reports started coming through of another plane ploughing into the second tower. My foot pressed harder on the accelerator, all thoughts of accidents banished from my mind.
Yet my hasty dash to Heathrow - and then Gatwick and, finally, Stansted - proved in vain. All flights into and out of the US and Canada were grounded.
It was the start of three of the most frustrating days of my professional life when I could only watch on televisions in airport lounges the unfolding tragedies in Washington, Pennsylvania and, most poignantly, New York - my favourite city of all - where I had been based in the Telegraph's bureau until a couple of years earlier.
I got the first flight out of the UK after the ban was lifted which left from Gatwick destined for Detroit. From there, a flight into New York was simple to arrange.
And, as the 737 made its final approach into La Guardia, the familiar Manhattan skyline appeared on the port side. Except now that most famous of landscapes was missing something: those two, spindly matchboxes that had loomed over the south end of the island for as long I had known it.
None of the passengers said anything. We just gawped in a self-conscious, almost guilty, silence at the toothless gap in the skyline and at the plume of smoke still wafting from it.
Over the next two weeks, I interviewed those who had survived and the husbands or wives of many of those who had not.
I spoke to Tony Blair, who seemed genuinely distraught by what he had seen, and I had to comfort my own photographer when he broke down in tears at a fire station where an entire watch of a dozen men had perished when the South Tower collapsed.
And I spoke to many ordinary New Yorkers, most of them shaken to the core by what had happened and all far more subdued than normally the case in the "city that never sleeps". Now they weren't sleeping for fear of the nightmares they might have.
New York had lost its swagger. Even taxi drivers seemed to have forgotten how to honk their horns and, unbelievably, some were even stopping to allow jaywalkers to cross the street.
And everyone was missing the physical presence of the twin towers.
I had forgotten how, on emerging from a building or subway station, you would involuntarily glance around and get your bearings from those impressively gaunt pieces of verticality to your south.
Yet, for all the quiet sadness and feelings of loss, there was a united grittiness among all the New Yorkers I met … a determination that, whatever had inspired the hate and violence in the men that had attacked them, their enemies would never prevail.
Not that I encountered any of the Islamophobia that some politicians would later generate and exploit. Rather, the feeling at the time was that, while New York might have lost its swagger, it just might have found its heart.