A braking system for a trailer of a vehicle having a towing vehicle and a trailer, the trailer having: at least four ground engaging wheels (12, 14, 16, 18), each having an associated brake actuator, the first and second wheels (12, 14) being supported on opposing sides of a first axle and the third and fourth wheels (16, 18) being supported on opposing sides of a second axle, the braking system having a control system including: a first braking valve system for supplying a first pressure to the brake actuator of the first wheel, a second braking valve system for supplying a second pressure to the brake actuator of the second wheel, and a second axle valve system for supplying a third pressure to the brake actuators of the third and fourth wheels (16, 18), characterised in that the control system is operable to control the first braking valve system independently from the second braking valve system such that the brake actuators of the first and second wheels (12, 14) are independently operable, and the second axle valve system is configured to adopt the pressure of a dominant braking valve system, so that the third pressure corresponds to the pressure from the dominant braking valve system, wherein the dominant braking valve system is the one of the first and second braking valve systems (22, 24) supplying the lowest pressure, wherein the control system is operable to implement a synchronisation threshold to control the difference between the first pressure and the second pressure. at least four ground engaging wheels (12, 14, 16, 18), each having an associated brake actuator, the first and second wheels (12, 14) being supported on opposing sides of a first axle and the third and fourth wheels (16, 18) being supported on opposing sides of a second axle, the braking system having a control system including: a first braking valve system for supplying a first pressure to the brake actuator of the first wheel, a second braking valve system for supplying a second pressure to the brake actuator of the second wheel, and a second axle valve system for supplying a third pressure to the brake actuators of the third and fourth wheels (16, 18), a first braking valve system for supplying a first pressure to the brake actuator of the first wheel, a second braking valve system for supplying a second pressure to the brake actuator of the second wheel, and a second axle valve system for supplying a third pressure to the brake actuators of the third and fourth wheels (16, 18), characterised in that the control system is operable to control the first braking valve system independently from the second braking valve system such that the brake actuators of the first and second wheels (12, 14) are independently operable, and the second axle valve system is configured to adopt the pressure of a dominant braking valve system, so that the third pressure corresponds to the pressure from the dominant braking valve system, wherein the dominant braking valve system is the one of the first and second braking valve systems (22, 24) supplying the lowest pressure, wherein the control system is operable to implement a synchronisation threshold to control the difference between the first pressure and the second pressure.