This is The Guardian.

This week, we're revisiting some of our favourite episodes from 2021.

And today, we return to a piece we ran over in the week of the 20th anniversary

of the 9-11 attacks on the US.

How a little-known terror network hatched a plot that shook the world.

And then nearly destroyed them.

It's a pretty dramatic picture we're looking at right now, fire in one of the world trade

center towers in the New York City. We don't know the cause of this fire or exactly

where it's coming from, but it appears there has been an ex.

Once you got over the shock that someone had flown planes into the twin towers,

it was inevitably the next question. Who did this?

It's not known who was behind them, nor is it clear how many people have died or have been injured.

I think the intelligence committee right now, especially the intelligence committees,

taking a view of it looks like, but we're not totally sure yet.

The search is underway for those who are behind these evil acts.

For a very small group of people, it was obvious.

I'm in September 11, 2001. How long does it take you to suspect

Al Qaeda might be involved? Oh, immediately.

Right away. Oh, right away.

Jason, where were you on September 11, and how quickly did you suspect it could be the work

of this group that you'd been tracking? I was in the offices of the observer,

and I was standing next to Paul Webster, who is now the editor, and we were watching the screen showing

...