A hammer drill comprising: a body in which is mounted a motor and a hammer mechanism which is driven by the motor when the motor is activated; a tool holder mounted on the front of the body and which is capable of holding a cutting tool, the hammer mechanism, when driven by the motor, capable of imparting impacts to the cutting tool, when held by the tool holder; a rear handle, moveably mounted on to the rear of the body via at least one movement control mechanism and which is capable of moving towards or away from the body; a biasing mechanism which biases the rear handle away from the body; wherein each movement control mechanism comprises: a first mount; a rod, having a longitudinal axis, rigidly connected at one of it ends to the first mount; and a second mount which slidingly engages with the rod at two distinct points of contact only along its length to allow the rod to slide relative to the second mount in a direction parallel to the longitudinal axis whilst preventing the rod from moving relative to second mount in a direction perpendicular to longitudinal axis; wherein one mount (70, 133, 136) is attached to the body and the other mount is attached to the rear handle; wherein the second mount comprises a first engaging portion (142; 164) which slidingly engages with the side of the rod and the rod comprises a second engaging portion which slidingly engages with a sliding surface formed on the second mount; characterised in that the position on the rod, where the first engaging portion slidingly engages the rod between the second engaging portion on the rod and the first mount so that the first engaging portion (142; 164) moves away from the second engaging portion as the handle moves towards the body, so that said points of engagement move apart as the handle moves towards the body; and in that the second mount comprises a tubular guide which surrounds the rod and slidingly engages with the side of the rod; and wherein the tubular guide has an inner surface which tapers outwardly or is convex along its length, the guide slidingly engaging the rod at its narrowest point d where it has the same dimensions as the outer diameter of the rod. a body in which is mounted a motor and a hammer mechanism which is driven by the motor when the motor is activated; a tool holder mounted on the front of the body and which is capable of holding a cutting tool, the hammer mechanism, when driven by the motor, capable of imparting impacts to the cutting tool, when held by the tool holder; a rear handle, moveably mounted on to the rear of the body via at least one movement control mechanism and which is capable of moving towards or away from the body; a biasing mechanism which biases the rear handle away from the body; wherein each movement control mechanism comprises: a first mount; a rod, having a longitudinal axis, rigidly connected at one of it ends to the first mount; and a second mount which slidingly engages with the rod at two distinct points of contact only along its length to allow the rod to slide relative to the second mount in a direction parallel to the longitudinal axis whilst preventing the rod from moving relative to second mount in a direction perpendicular to longitudinal axis; a first mount; a rod, having a longitudinal axis, rigidly connected at one of it ends to the first mount; and a second mount which slidingly engages with the rod at two distinct points of contact only along its length to allow the rod to slide relative to the second mount in a direction parallel to the longitudinal axis whilst preventing the rod from moving relative to second mount in a direction perpendicular to longitudinal axis; wherein one mount (70, 133, 136) is attached to the body and the other mount is attached to the rear handle; wherein the second mount comprises a first engaging portion (142; 164) which slidingly engages with the side of the rod and the rod comprises a second engaging portion which slidingly engages with a sliding surface formed on the second mount; characterised in that the position on the rod, where the first engaging portion slidingly engages the rod between the second engaging portion on the rod and the first mount so that the first engaging portion (142; 164) moves away from the second engaging portion as the handle moves towards the body, so that said points of engagement move apart as the handle moves towards the body; and in that the second mount comprises a tubular guide which surrounds the rod and slidingly engages with the side of the rod; and wherein the tubular guide has an inner surface which tapers outwardly or is convex along its length, the guide slidingly engaging the rod at its narrowest point d where it has the same dimensions as the outer diameter of the rod.