A vehicle speed control system for controlling a vehicle having a plurality of wheels. The vehicle speed control system is configured to automatically control the speed of the vehicle in dependence on an input target set-speed. The system carries out a method that includes: applying torque to at least one of the plurality of wheels; receiving a user input of a target set-speed at which the vehicle is intended to travel; and applying torque to the at least one of the plurality of wheels for propelling the vehicle at a vehicle control speed. The system further controls the vehicle control speed as a function of at least one of the instantaneous vehicle speed and the terrain over which the vehicle is travelling.