A fluid pressure control system comprising a first chamber, the pressure in which is to be controlled, a second chamber and a valve means for controlling communication between the first and second chambers. A controller is arranged such that, if the pressure in the first chamber differs from a required pressure, the controller i) operates the valve means to close off communication between the first and second chambers, ii) varies the pressure in the second chamber, iii) opens communication between the first and second chambers to deliver a discrete pressure step to the first chamber, and, iv) repeats i) to iii) until the pressure in the first chamber reaches a required level.