An aqueous dispersion of pigmented opacifying polymer particles, the particles comprising: i. an inorganic core comprising dispersed inorganic pigment particle and a dispersant ii. a first layer of base-swellable polymer comprising acid groups encapsulating the core iii. a second layer of non-base-swellable polymer encapsulating the first layer wherein the dispersant comprises or consists of hydroxyl moieties; and carboxyl groups derived from itaconic acid.