This Sunday marks the tenth anniversary of an act of terrorism that changed the world forever.
At the time, I can recall clearly standing in the news room at BBC South Today, watching with incredulity as first one and then a second plane tore into the two buildings.
Two other planes came down, one on the Pentagon, the other in a field near Pittsburgh.
A total of nearly 3,000 people were murdered.
The attack tore at the very soul of the United States, until that point so self-assured and dominant.
The sheer audacity of this outrage shook the world.
Since then, wars of retribution in first Iraq and then Afghanistan have claimed many more lives.
Constant vigilance, subsequently, has altered our lives beyond our imagination.
At airports onerous security causes long delays and often inconvenience for passengers.
Across the world, retinal scans and fingerprinting are the norm at many border crossings.
Satellites constantly scan the earth for small anomalies which could spell danger.
We are all monitored, warned and advised about potential dangers at home and abroad.
In America, every street corner bears the sign: “If you see something, say something.”
But, we must be careful.
An over-reaction is what our enemies want, to undermine the very freedoms that millions have died defending in two World Wars and many other conflicts.
I believe that while we must remain vigilant, we must never be cowed.
This and other terrorist attacks only serve to remind us that freedom does not come cheaply and sadly many more people will die in the years ahead as we continue to stand up for what we believe in.
All too frequently it is the innocent who find themselves in the firing line and all we can do is mourn their loss and strengthen our resolve.