A steering column assembly comprising: a telescopic shroud having an outer shroud portion and an inner shroud portion, an end of the inner shroud portion extending into the outer shroud portion, a clamp rail fixed to the inner shroud portion including a slot that extends axially along the inner shroud portion, the slot defining two opposing walls which each carry a row of teeth, the two rows thereby being spaced apart from one another with the teeth extending towards each other; a clamp bolt that extends perpendicular to the shroud that may be rotated around its long axis by operation of a locking lever, a toothed block that is connected to the clamp bolt and is displaced on rotation of the clamp bolt, the toothed block having a row of teeth on each side, the pitch between teeth of each row being equal to, or a whole multiple of, the pitch of the teeth of the corresponding row of the slot, the toothed block being supported by a carrier that moves in response to rotation of the clamp bolt to in turn move the toothed block between a clamped position in which the toothed block is located in the slot with the teeth of the toothed block in the same plane as the teeth of the slot and an unclamped position in which the toothed block is held such that the teeth of the toothed block are out of the plane of the teeth of the slot; the carrier supporting the toothed block such that the toothed block is free to move from side to side when in the slot, the teeth of the two rows of teeth of the slot and the teeth of the two rows of teeth of the toothed block are shaped such that for any given position of the outer shroud portion relative to the inner shroud portion the toothed block is free to move into the slot when the carrier is moved into the clamped position from the unclamped position without being blocked by the teeth of the toothed block striking the teeth of the slot, and characterized in that the teeth of a first row of the slot and the corresponding teeth of the toothed block when in flank to flank contact prevent axial movement of the toothed block along the slot in a direction corresponding to a telescopic collapse of the shroud and in that the teeth of a second row of the slot and the corresponding teeth of the toothed block permit axial movement of the toothed block along the slot in a direction corresponding to a collapse of the shroud whilst applying a thrust to the toothed block that moves the toothed block sideways across the slot so that the flanks of the teeth of the first row face the flanks of the corresponding teeth of the toothed block. a telescopic shroud having an outer shroud portion and an inner shroud portion, an end of the inner shroud portion extending into the outer shroud portion, a clamp rail fixed to the inner shroud portion including a slot that extends axially along the inner shroud portion, the slot defining two opposing walls which each carry a row of teeth, the two rows thereby being spaced apart from one another with the teeth extending towards each other; a clamp bolt that extends perpendicular to the shroud that may be rotated around its long axis by operation of a locking lever, a toothed block that is connected to the clamp bolt and is displaced on rotation of the clamp bolt, the toothed block having a row of teeth on each side, the pitch between teeth of each row being equal to, or a whole multiple of, the pitch of the teeth of the corresponding row of the slot, the toothed block being supported by a carrier that moves in response to rotation of the clamp bolt to in turn move the toothed block between a clamped position in which the toothed block is located in the slot with the teeth of the toothed block in the same plane as the teeth of the slot and an unclamped position in which the toothed block is held such that the teeth of the toothed block are out of the plane of the teeth of the slot; the carrier supporting the toothed block such that the toothed block is free to move from side to side when in the slot, the teeth of the two rows of teeth of the slot and the teeth of the two rows of teeth of the toothed block are shaped such that for any given position of the outer shroud portion relative to the inner shroud portion the toothed block is free to move into the slot when the carrier is moved into the clamped position from the unclamped position without being blocked by the teeth of the toothed block striking the teeth of the slot, and characterized in that the teeth of a first row of the slot and the corresponding teeth of the toothed block when in flank to flank contact prevent axial movement of the toothed block along the slot in a direction corresponding to a telescopic collapse of the shroud and in that the teeth of a second row of the slot and the corresponding teeth of the toothed block permit axial movement of the toothed block along the slot in a direction corresponding to a collapse of the shroud whilst applying a thrust to the toothed block that moves the toothed block sideways across the slot so that the flanks of the teeth of the first row face the flanks of the corresponding teeth of the toothed block.