A hammer drill comprising: a body in which is mounted a motor and a hammer mechanism; the hammer mechanism being driven by the motor when the motol, is activated; a tool holder mounted on the front of the body and which is capable of holding a cutting tool, the hammer mechanisn, when driven by the motor, capable of imparting impacts to a cutting tool, when held by the tool holder; a rear handle moveably connected to the rear of the body and which is capable of moving towards or away from the body; wherein the rear handle comprises a centre grip section and two end connection sections, one end connection section being attached to one end of the centre grip section, the other end connection section being connected to the other end of the centre grip section, each end connection section being slideably mounted on an arm, which projects rearward from the body so that they can slide along the arms towards or away from the body; a movement control mechanism which controls the movement of the handlel relative to the body; a dampening mechanism which reduces the vibration transferred from the body to the rear handle; wherein the movement control mechanism is mounted inside the rear handle characterised in that the movement control mechanism connects between the arms and the handle and comprises: an axle rotatably mounted about its longitudinal axis inside of the grip section; two connectors, both connectors being rigidly connected to the axle wherein the axle is pivotally mounted within the handle so that it moves away from or towards the body with the handle as the handle slides on the arms; each of the connectors being pivotally connected about a pivot axis to an arm so that the distance of the pivot axes of the connectors from the body remain constant, the movement control mechanism ensuring that the two end connection sections move towards or away from the body in unison to prevent angular movement of the centre grip section relative to the body. a body in which is mounted a motor and a hammer mechanism; the hammer mechanism being driven by the motor when the motol, is activated; a tool holder mounted on the front of the body and which is capable of holding a cutting tool, the hammer mechanisn, when driven by the motor, capable of imparting impacts to a cutting tool, when held by the tool holder; a rear handle moveably connected to the rear of the body and which is capable of moving towards or away from the body; wherein the rear handle comprises a centre grip section and two end connection sections, one end connection section being attached to one end of the centre grip section, the other end connection section being connected to the other end of the centre grip section, each end connection section being slideably mounted on an arm, which projects rearward from the body so that they can slide along the arms towards or away from the body; a movement control mechanism which controls the movement of the handlel relative to the body; a dampening mechanism which reduces the vibration transferred from the body to the rear handle; an axle rotatably mounted about its longitudinal axis inside of the grip section; two connectors, both connectors being rigidly connected to the axle wherein the axle is pivotally mounted within the handle so that it moves away from or towards the body with the handle as the handle slides on the arms; each of the connectors being pivotally connected about a pivot axis to an arm so that the distance of the pivot axes of the connectors from the body remain constant, the movement control mechanism ensuring that the two end connection sections move towards or away from the body in unison to prevent angular movement of the centre grip section relative to the body.