An electro-optic display comprises a bistable electro-optic medium, a plurality of pixel electrodes, with associated non-linear elements, and a common electrode, disposed on opposed sides of the electro-optic medium. The display has a writing mode, in which at least two different voltages are applied to different pixel electrodes, and a non-writing mode in which the voltages applied to the pixel electrodes are controlled so that any image previously written on the electro-optic medium is substantially maintained. The display is arranged to apply to the common electrode a first voltage when the display is in its writing mode and a second voltage, different from the first voltage, when the display is in its non-writing mode.