Over the afternoon, further reports began to come in, but I was working in an office with very restricted bandwidth and no radio and so we couldn't really keep up. I only got the full brunt of it on the drive back home, listening to the car radio.
I had set the video at home to record Channel 4's showing of That Hamilton Woman starring Laurence Olivier and Vivien Leigh. During one ad break, Peter Sissons popped up to break the news; at the next ad break, the film was put on hold and it became non-stop New York footage. I had to wait for Channel 4 to repeat it months later to learn how it ended (though I had a shrewd suspicion).
The next day, Classic FM had suspended its usual programme and was just playing appropriate requests. Someone requested "Lacrimosa" from Priesner's Requiem for a Friend, and that was the point my eyes filled with tears and I almost had to pull over.
This wasn't how we wanted 2001 to be, was it? We wanted a thriving moonbase and orbital colony and all the petty affairs of mankind put behind us. Instead, apparently, exactly one American was off-world at the time, up in the ISS and all this was going on below. In the unlikely event of an alien intelligence monitoring us from the Moon, I think the gist of the report home would have been, "avoid." But to be quite honest, that describes most days before and since.
Personally I think 9/11 was also a Titanic moment - a foreseeable, avoidable tragedy that nonetheless saved thousands more lives than were lost. After the Titanic, ships carried enough lifeboats. Before 9/11 you could have got an elephant through US customs but not after; 9/11 may well have prevented the Great Al Qaeda Nuclear Strike of 2015. As part of the package we also got less than fond memories of George W. Bush, an extremely dodgy war in Iraq, the Department of Homeland Security ... but to be quite frank, if we hadn't had those then we would have had something else. We've never lived in a paradise and, this side of the end of time and space, we never will.
Sometime after 9/11 we heard in the office that Sarah Ferguson had apparently had a meeting scheduled in the WTC for later that day. There was a moment's thoughtful silence among all of us, and then the boss exclaimed, "Shame on you for what you were just thinking!"