Abstract: A shaft clamp assembly (10) includes a bracket having a tubular member adapted to receive a shaft, for example the shaft of an umbrella, a device for mounting the tubular member (11) to a structure, for example a table, and a clamping element (15), the clamping element being operable to secure the shaft to the tubular member, and wherein the internal wall of the tubular member is provided with at least two shaft contact surfaces, their arrangement being such that a triangle of forces is generated between the clamping element and the shaft contact surfaces to secure the shaft to the tubular member when the clamping element is operated.