A wastegate assembly for a turbine comprising: a turbine wheel; a turbine housing defining at least one gas inlet upstream of the turbine wheel and a turbine outlet downstream of the turbine wheel; and a wastegate chamber communicating with the at least one gas inlet via one or more wastegate ports; the wastegate assembly comprising: a support member (160; 260; 360; 460; 560); and at least one valve member (150, 250; 350; 550) for blocking a corresponding wastegate port, the or each valve member being mounted on the support member (160; 260; 360; 460; 560) via a pin portion (154; 254; 354; 554) of the valve member for articulation about the support member (160; 260; 360; 460; 560), having a central axis (151; 251; 351; 551) and comprising a sealing portion (152; 252; 352; 552) which extends away from the axis to an outer edge of the valve member, the sealing portion having a sealing surface (153; 253; 353 transverse to the axis for blocking one of the one or more wastegate ports upon the sealing surface of the valve member being pressed against a rim of the wastegate port, a washer being attached to the pin portion (154; 254; 354; 554) of the valve member on the opposite side of the support member from the sealing portion of the valve member; a rear surface of the sealing portion opposite to the sealing surface including an limit area (156; 256; 356; 556) of the valve member radially inward of the outer edge of the sealing portion of the valve member, the limit area of the valve member encircling the pin portion of the valve member and at each angular position about the pin portion providing a respective limit point being arranged to limit articulation of the valve member in a respective plane by colliding with a corresponding respective limit point on a limit area (165; 265; 365; 465; 565) of the support member, the limit area of the support member being a portion of a front surface of the support member facing towards the sealing portion of the valve member; the at least one valve member (150, 250; 350; 550) further comprising a support surface (155; 255; 355; 555) between the pin portion and the limit area of the valve member, the support surface bearing against a corresponding support surface (163; 263; 363; 565) of the support member, the two support surfaces being portions of respective spheres; the limit area of the or each valve member being rotationally symmetric about the central axis, and the limit area of the support member being rotationally symmetric about a second axis, whereby the degree of limitation of the articulation from a position in which the central axis and second axis are coincident, is rotationally symmetric about the axes. a support member (160; 260; 360; 460; 560); and at least one valve member (150, 250; 350; 550) for blocking a corresponding wastegate port, the or each valve member being mounted on the support member (160; 260; 360; 460; 560) via a pin portion (154; 254; 354; 554) of the valve member for articulation about the support member (160; 260; 360; 460; 560), having a central axis (151; 251; 351; 551) and comprising a sealing portion (152; 252; 352; 552) which extends away from the axis to an outer edge of the valve member, the sealing portion having a sealing surface (153; 253; 353 transverse to the axis for blocking one of the one or more wastegate ports upon the sealing surface of the valve member being pressed against a rim of the wastegate port, a washer being attached to the pin portion (154; 254; 354; 554) of the valve member on the opposite side of the support member from the sealing portion of the valve member; a rear surface of the sealing portion opposite to the sealing surface including an limit area (156; 256; 356; 556) of the valve member radially inward of the outer edge of the sealing portion of the valve member, the limit area of the valve member encircling the pin portion of the valve member and at each angular position about the pin portion providing a respective limit point being arranged to limit articulation of the valve member in a respective plane by colliding with a corresponding respective limit point on a limit area (165; 265; 365; 465; 565) of the support member, the limit area of the support member being a portion of a front surface of the support member facing towards the sealing portion of the valve member; the at least one valve member (150, 250; 350; 550) further comprising a support surface (155; 255; 355; 555) between the pin portion and the limit area of the valve member, the support surface bearing against a corresponding support surface (163; 263; 363; 565) of the support member, the two support surfaces being portions of respective spheres; the limit area of the or each valve member being rotationally symmetric about the central axis, and the limit area of the support member being rotationally symmetric about a second axis, whereby the degree of limitation of the articulation from a position in which the central axis and second axis are coincident, is rotationally symmetric about the axes.