A compressor for a gas turbine engine, the compressor comprising: an annular inlet duct having an annular hub side wall and an annular shroud side wall extending around the hub side wall spaced apart therefrom; at least one rotor having an array of blades mounted on a rotatable shaft, the blades extending across a flow path in fluid communication and in alignment with the inlet duct; and a plurality of circumferentially spaced apart inlet guide vanes each comprising: a hub end configured to be received in a hub side of a gas path; a tip end configured to be received in an opposed side of the gas path, the hub and tip ends (44, 46) being aligned and defining a pivot axis of the vane extending therethrough; and an airfoil portion extending between the hub end and the tip end, the airfoil portion defining opposed leading and trailing edges (50, 52), the airfoil portion being twisted such that at each location of the airfoil portion along the axis, an angle (α) is defined between a respective chord extending between the leading and trailing edges (50, 52) and a same reference plane containing the pivot axis; wherein the plurality of inlet guide vanes extends across the inlet duct from the hub side wall to the shroud side wall, the same reference plane extending radially with respect to the compressor, the angle (α) varying from a minimum value near the hub side wall to a maximum value near the shroud side wall, the angle (α) being measured along a direction of rotation of the rotor; characterised in that: the inlet duct has an upstream portion extending substantially radially with respect to the compressor and a downstream portion extending substantially axially with respect to the compressor, the pivot axis of each vane extending substantially axially; and in that the angle (α) varies non-linearly along the pivot axis as a function of a distance from the hub end. an annular inlet duct having an annular hub side wall and an annular shroud side wall extending around the hub side wall spaced apart therefrom; at least one rotor having an array of blades mounted on a rotatable shaft, the blades extending across a flow path in fluid communication and in alignment with the inlet duct; and a plurality of circumferentially spaced apart inlet guide vanes each comprising: a hub end configured to be received in a hub side of a gas path; a tip end configured to be received in an opposed side of the gas path, the hub and tip ends (44, 46) being aligned and defining a pivot axis of the vane extending therethrough; and an airfoil portion extending between the hub end and the tip end, the airfoil portion defining opposed leading and trailing edges (50, 52), the airfoil portion being twisted such that at each location of the airfoil portion along the axis, an angle (α) is defined between a respective chord extending between the leading and trailing edges (50, 52) and a same reference plane containing the pivot axis; wherein the plurality of inlet guide vanes extends across the inlet duct from the hub side wall to the shroud side wall, the same reference plane extending radially with respect to the compressor, the angle (α) varying from a minimum value near the hub side wall to a maximum value near the shroud side wall, the angle (α) being measured along a direction of rotation of the rotor; characterised in that: the inlet duct has an upstream portion extending substantially radially with respect to the compressor and a downstream portion extending substantially axially with respect to the compressor, the pivot axis of each vane extending substantially axially; and in that the angle (α) varies non-linearly along the pivot axis as a function of a distance from the hub end. the inlet duct has an upstream portion extending substantially radially with respect to the compressor and a downstream portion extending substantially axially with respect to the compressor, the pivot axis of each vane extending substantially axially; and in that the angle (α) varies non-linearly along the pivot axis as a function of a distance from the hub end.