A pile or ground anchor (100, 200, 300) for a building or structure, comprising an elongate shaft (102, 202, 302) having a longitudinal axis for positioning in a borehole (10, 20, 30), two or more sidewalls (106, 206, 306) defining a substantially tubular structure surrounding a length of the elongate shaft for engaging the borehole, one or more connectors (104, 204, 304) disposed along the elongate shaft, connecting the sidewalls to the elongate shaft, at least some of the one or more connectors being moveable relative to or along the elongate shaft for moving the sidewalls, the sidewalls being moveable or extendible from i) a retracted configuration in which the sidewalls are disposed proximate to the shaft, the diameter of the tubular structure being suitable for insertion into a borehole, to ii) a deployed configuration in which the sidewalls are radially spaced from the longitudinal axis of the shaft, relative to the retracted configuration, in use the two or more sidewalls bearing against and substantially radially expanding a corresponding length of the borehole by movement into the deployed configuration, such that the diameter of the tubular structure in the deployed configuration is greater than the original diameter of the borehole, and characterised in that an elongate sleeve (130, 330) is connected to the uppermost connector (104a, 304a) on the elongate shaft, wherein during installation one of the elongate shaft and sleeve is adapted to be moveable by rotation or translation relative to the other of the elongate shaft and sleeve, and the other of the elongate shaft and sleeve is securable against the corresponding rotation or translation. an elongate shaft (102, 202, 302) having a longitudinal axis for positioning in a borehole (10, 20, 30), two or more sidewalls (106, 206, 306) defining a substantially tubular structure surrounding a length of the elongate shaft for engaging the borehole, one or more connectors (104, 204, 304) disposed along the elongate shaft, connecting the sidewalls to the elongate shaft, at least some of the one or more connectors being moveable relative to or along the elongate shaft for moving the sidewalls, the sidewalls being moveable or extendible from i) a retracted configuration in which the sidewalls are disposed proximate to the shaft, the diameter of the tubular structure being suitable for insertion into a borehole, to ii) a deployed configuration in which the sidewalls are radially spaced from the longitudinal axis of the shaft, relative to the retracted configuration, in use the two or more sidewalls bearing against and substantially radially expanding a corresponding length of the borehole by movement into the deployed configuration, such that the diameter of the tubular structure in the deployed configuration is greater than the original diameter of the borehole, and characterised in that an elongate sleeve (130, 330) is connected to the uppermost connector (104a, 304a) on the elongate shaft, wherein during installation one of the elongate shaft and sleeve is adapted to be moveable by rotation or translation relative to the other of the elongate shaft and sleeve, and the other of the elongate shaft and sleeve is securable against the corresponding rotation or translation.