A fuel injection system for supplying pressurised fuel to a fuel injector (50), the fuel injection system comprising an accumulator volume (59) for supplying fuel at a first injectable pressure level (P1) to the fuel injector (50) through a fuel supply passage (52), pump means (63) for increasing the pressure of fuel supplied to the injector (50) to a second injectable pressure level (P2), and valve means (62, 162, 262, 362) operable between a first position in which fuel at the first injectable pressure level (P1) is supplied to the injector (50) and a second position in which communication between the injector (50) and the accumulator volume (59) is broken so as to permit fuel at the second injectable pressure (P2) to be supplied to the injector. The injection system may include valve means in the 15 form of a three-position valve (262) or may include a shut off valve (464; 1464) for controlling the supply of fuel through the fuel supply passage (52).