A taxi driver who witnessed the aftermath of the incident in Edmonton, north London, told ITV News he saw police force their way into a house on Nightingale Road.
"They broke the door down and brought a man out," he said.
"There were dozens of police cars and a helicopter."
He added: "It's really worrying. It's very scary - we're always on the lookout."
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High pressure will help keep conditions relatively quiet through the course of this week.