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On Wednesday afternoon a police officer was stabbed and killed by an assailant outside the British Houses of Parliament.
A car also ploughed into a crowd of people on Westminster bridge, killing one woman and injuring many. Three French teenagers on a school trip to London were also badly injured in the attack.
At present, five are confirmed dead and 40 people have been injured.
The political editor of the Independent, Joe Watts, whose office window overlooks where the attack took place, shared his thoughts on the tragic attack.
Explaining the developing situation via Twitter, Watts commended the security and ambulances services for their work.
Initially, the car striking the crowds of tourists and Westminster workers was a harrowing experience.
The screams heard when the car ploughed through people outside Westminster were unlike any I have ever heard — Joe Watts (@Joe Watts)
As the incident was still unfolding, while some people ran away, many others rushed to it, to see was happening — Joe Watts (@Joe Watts)
Watching armed police and paramedics work around the victims and assailant so professionally while most people were dumbstruck was amazing — Joe Watts (@Joe Watts)
I have never seen so many officers and paramedics descend on to one place so quickly — Joe Watts (@Joe Watts)
...odd atmosphere in here. Some ppl working, others looking shaken others angry at being herded around the place. — Joe Watts (@Joe Watts)
...when they struck he dropped to the floor immediately... — Joe Watts (@Joe Watts)
....paramedics worked, giving him cpr for a sustained period... — Joe Watts (@Joe Watts)
....at the same time a second team worked frantically nearby on the officer who was stabbed... — Joe Watts (@Joe Watts)
You can follow all the latest developments in the Westminster attack using the Independent's live page.
More: Westminster terror incident: What we know and what we don't know
Watch:London attack: What you need to know