V: Remember, remember, the fifth of November, The gunpowder treason and plot. I know of no reason why the gunpowder treason should ever be forgot.
When the detective places the item on his desk, to confuse the scanners in the area, at first he places it on a high pile of CDs. In the next shot the item is in a different location on the desk.
In the scene where Evey gets her hair cut, it was Natalie Portman's real hair they cut. They had only one shot to capture that scene, and everybody was quite nervous if the scene would turn out usable.