Pressure relief valve for a hydraulic press tool, comprising: a valve body; a fluid circulation channel having an inlet portion for receiving pressurised fluid from an inlet side of the pressure relief valve and also an outlet portion (39, 40) for enabling the fluid to exit from the pressure relief valve; a needle and a seat, the needle and the seat being movable relative to the valve body between a closed position in which the needle is in contact with the seat in order to close the channel and an open position in which the needle is at a distance from the seat in order to allow the pressurised fluid to circulate in the channel and thereby exit the pressure relief valve through the outlet portion (39, 40) thereof; a stop comprising a surface for limiting movement of the needle towards the seat and another surface for limiting movement of the seat towards the needle; an O-ring seal for restricting the passage of pressurised fluid between the seat and the valve body from the inlet side of the pressure relief valve; wherein the pressure relief valve is configured such that, in use, when the pressure of fluid on the inlet side thereof reaches a predetermined threshold the needle is moved by the pressurised fluid to the open position, following which the fluid causes a movement of the seat relative to the valve body away from the needle to open the channel for enabling the fluid to circulate in the channel and thereby exit from the pressure relief valve and the sum of the forces of the pressurised fluid acting on the seat and the force of the O-ring seal on the seat restricts the seat from returning towards the needle in order to maintain the circulation of the fluid in the channel. a valve body; a fluid circulation channel having an inlet portion for receiving pressurised fluid from an inlet side of the pressure relief valve and also an outlet portion (39, 40) for enabling the fluid to exit from the pressure relief valve; a needle and a seat, the needle and the seat being movable relative to the valve body between a closed position in which the needle is in contact with the seat in order to close the channel and an open position in which the needle is at a distance from the seat in order to allow the pressurised fluid to circulate in the channel and thereby exit the pressure relief valve through the outlet portion (39, 40) thereof; a stop comprising a surface for limiting movement of the needle towards the seat and another surface for limiting movement of the seat towards the needle; an O-ring seal for restricting the passage of pressurised fluid between the seat and the valve body from the inlet side of the pressure relief valve; wherein the pressure relief valve is configured such that, in use, when the pressure of fluid on the inlet side thereof reaches a predetermined threshold the needle is moved by the pressurised fluid to the open position, following which the fluid causes a movement of the seat relative to the valve body away from the needle to open the channel for enabling the fluid to circulate in the channel and thereby exit from the pressure relief valve and the sum of the forces of the pressurised fluid acting on the seat and the force of the O-ring seal on the seat restricts the seat from returning towards the needle in order to maintain the circulation of the fluid in the channel.