New Major Terrorist Attack in London?

I hope not, but initial reports from the Telegraph are looking pretty bad:
One person has been arrested after a vehicle struck pedestrians, leaving “a number of casualties” in north London.
Officers were called at 12.20am on Monday to Seven Sisters Road, the Metropolitan Police said.
London Ambulance Service said: “We have sent a number of resources to an incident in Seven Sisters Road.”
The incident reportedly happened close to Finsbury Park mosque.
All hell breaking loose in Finsbury park. pic.twitter.com/sYE9PBhsi6
— ben tovey (@ben_tovey) June 18, 2017
Consider this the overnight thread.