Looks like there was some gunfire outside the UK parliament. And a 2nd possibly related/unrelated hit and run that mowed down 5 people on Westminster bridge. Edit: It's all being treated as related and has been officially called a terrorist incident attack.
This should surprise absolutely no one, but ISIS claims responsibility: http://www.cnn.com/2017/03/23/europe/london-attack/
Shouldn't there be a distinction though... between crazy people buying into propaganda and actual trained ISIS fighters. Same with the Florida nightclub shooting. That turned out to be a repressed gay guy snapping who happened to view some terrorist propaganda. It seems like giving them too much credit which they actually want.
Everyone else being so racist, Islamophobic, and transpregnantphobic made them do it. Or at least that's what I expect to hear from the media here.