In the Doctor Who episode Blink the Doctor sets up a trap for the four Weeping Angels seen in the episode by tricking all four to converge on the Tardis as it dematerializes, so once it's gone, they are all looking at each other.
This is in the basement of an abandon house. While there is some light coming in, there could be times, such as moonless and cloudy nights, where there will be almost no light available and it's possible if the house were boarded up even more securely, that the basement could be in total blackness.
Would the Weeping Angels still be trapped because they're looking at each other, or once they're in pitch black, would they no longer see each other and - in their awareness - have time to cover their eyes and avoid looking into each other?