Aqueous polyurethane dispersion in which the polyurethane is made by chain-extension of a prepolymer, and optionally including another polymer (particularly acrylic), wherein the prepolymer incorporates a dimer acid-based polyesterpolyol and also a low molecular weight cycloaliphatic and/or aromatic polyol and/or polyacid and wherein any low molecular weight cycloaliphatic or aromatic polyol is incorporated as a component of the polyester polyol and/or is used as such in the prepolymer synthesis, and any low molecular weight cycloaliphatic or aromatic polyacid is only or substantially only used as such in the prepolymer synthesis.