Liquid storage system

A liquid storage system, such as an aircraft fuel tank, comprises a tank 16 for containing a liquid. The tank encloses a liquid storage space 14 and a tank liner 18 is fixedly attached to an internal surface of the tank. The tank liner comprises a plurality of elements 22, each element having a hardness value of 2GPa or above, and a binder material 20 in which the plurality of elements are embedded. The elements have a higher hardness value than the binder material. A distance between a first element and the internal surface of the tank in a direction normal to the internal surface of the tank is different to a distance between a second element and the internal surface of the tank. The elements may be spherical elements and may be formed of ceramic, metal or metal alloy. The binder material may be formed from rubber or a polymer. The elements may be uniformly distributed throughout the binder material. The binder material may be more flexible than the walls of the tank.