FUEL STORAGE SYSTEMS

There is provided a fuel storage system. The fuel storage system (2) comprises a fuel tank (21) configured to store a liquid fuel; a controllable pressure source (22) for altering the pressure in an ullage space (211) of the fuel tank; and a controller (24). The controller is configured to determine a target pressure for the ullage space at a given time based on information relating to a temperature of fuel inside the fuel tank at the given time; and to control the pressure source such as to cause the pressure in the ullage space to be substantially equal to the target pressure.