The present invention relates to a method of controlling an electrical power network (10) in dependence on a sudden event which is liable to lead to further loss or excess of generation or load. The electrical power network (10) comprises plural controllers (20, 22) with each controller being configured to provide for control of controllable apparatus (30) connected to the electrical power network at a different respective location in the electrical power network. The method comprises determining the occurrence of a sudden event that is liable to lead to further loss or excess of generation or load in the electrical power network or part of the electrical power network. The method further comprises receiving plural substantially synchronised quantities in each of the plural controllers (20, 22), each of the plural quantities corresponding to at least one of frequency and angle at a respective one of plural different locations in the electrical power network. The method yet further comprises generating a control output from each of the controllers (20, 22) in dependence on the received plural quantities, each control output being for control of its respective controllable apparatus (30), each controller being operative to generate the control output independent of operation of any other controller and on an ongoing basis in dependence on ongoing receipt of the plural quantities.