A control system for controlling operation of a trailer brake system associated with an agricultural vehicle-trailer combination, the control system comprising a vehicle control unit, and being configured to determine an operational cycle of the trailer brake system and control operation of the trailer brake system in accordance with the determined operational cycle; wherein the operational cycle is split into: a first time period in which the control system is operable to generate and output control signals to the trailer brake system for controlling the trailer brake system in accordance with a primary operational strategy; and a second time period in which the control system is operable to forward control signals for controlling the trailer brake system in accordance with a secondary operational strategy; wherein the secondary operational strategy comprises reducing a braking force applied by the trailer brake system at the end of the first time period such that no braking force is applied by the trailer brake system to the vehicle-trailer combination at the end of the second time period characterized in that the control system is configured to determine the rate at which the braking force is reduced in accordance with the second operational strategy in dependence on one or more of: a processing cycle time of the vehicle control unit; a length of the second time period; and a pressure level associated with the trailer brake system at the end of the first time period. wherein the operational cycle is split into: a first time period in which the control system is operable to generate and output control signals to the trailer brake system for controlling the trailer brake system in accordance with a primary operational strategy; and a second time period in which the control system is operable to forward control signals for controlling the trailer brake system in accordance with a secondary operational strategy; a first time period in which the control system is operable to generate and output control signals to the trailer brake system for controlling the trailer brake system in accordance with a primary operational strategy; and a second time period in which the control system is operable to forward control signals for controlling the trailer brake system in accordance with a secondary operational strategy; wherein the secondary operational strategy comprises reducing a braking force applied by the trailer brake system at the end of the first time period such that no braking force is applied by the trailer brake system to the vehicle-trailer combination at the end of the second time period characterized in that the control system is configured to determine the rate at which the braking force is reduced in accordance with the second operational strategy in dependence on one or more of: a processing cycle time of the vehicle control unit; a length of the second time period; and a pressure level associated with the trailer brake system at the end of the first time period. a processing cycle time of the vehicle control unit; a length of the second time period; and a pressure level associated with the trailer brake system at the end of the first time period.