In this otherwise lopsided article about security cameras, this one quote stands out:

But Steve Swain, who served for years with the London Metropolitan Police and its counter-terror operations, doubts the power of cameras to deter crime.

“I don’t know of a single incident where CCTV has actually been used to spot, apprehend or detain offenders in the act,” he said, referring to the London system. Swain now works for Control Risk, an international security firm.

Asked about their role in possibly stopping acts of terror, he said pointedly: “The presence of CCTV is irrelevant for those who want to sacrifice their lives to carry out a terrorist act.”

[…]

Swain does believe the cameras have great value in investigation work. He also said they are necessary to reassure the public that law enforcement is being aggressive.

“You need to do this piece of theater so that if the terrorists are looking at you, they can see that you’ve got some measures in place,” he said.