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, a carrier element that supports the toothed block and is movable in response to rotation of the clamp bolt to in turn move the toothed block between a clamped position in which the block is located in the slot with teeth of the 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 block are out of the plane of the teeth of the slot; and in which the carrier element is free to move from side to side relative to the slot; and characterised by further comprising a frangible pin that secures the toothed block to the carrier element, the frangible pin having a first end located in a bore in the toothed block and a second end located in a bore in the carrier element, the toothed block being supported on a shoulder of the frangible pin, and in which a clearance is provided between the frangible pin and the walls of one of the bores (198, 200) to permit side to side movement of the toothed block relative to the carrier element. 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, a carrier element that supports the toothed block and is movable in response to rotation of the clamp bolt to in turn move the toothed block between a clamped position in which the block is located in the slot with teeth of the 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 block are out of the plane of the teeth of the slot; and in which the carrier element is free to move from side to side relative to the slot; and characterised by further comprising a frangible pin that secures the toothed block to the carrier element, the frangible pin having a first end located in a bore in the toothed block and a second end located in a bore in the carrier element, the toothed block being supported on a shoulder of the frangible pin, and in which a clearance is provided between the frangible pin and the walls of one of the bores (198, 200) to permit side to side movement of the toothed block relative to the carrier element.