There are moments in history that are so devastating they are forever seared into memory and the world comes to a standstill in shock and horror.
Much like the death of Princess Diana, or assassination of JFK, you will always remember where you were when you first heard the news of 9/11, but it is perhaps even more shocking due to the panic that ensued where the world felt under siege and - as MailOnline columnist Piers Morgan remembers - it felt like 'armageddon'.
On the morning of September 11, 2001, 19 Al-Qaeda terrorists successfully hijacked four California-bound planes, and by 9.30am the World Trade Centre, one of New York City's most famous landmarks, had been hit, hundreds killed and many more trapped in the floors above.
Many watching the scenes on televisions across the globe believed initially it was a tragic accident - but it quickly became apparent it was an act of war, undertaken to strike fear and devastation into the hearts of Americans, and indeed the rest of the world.
Now, 20 years later, politicians, public figures and TV personalities have shared with MailOnline where they were when they first heard the news that day and the shock and emotion that quickly followed.
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