An axial flow compressor (16) comprises a plurality of variable stator vanes (32) circumferentially spaced apart and extending radially. Each variable stator vane (32) is rotatably mounted on a compressor casing (28). A control ring (38) surrounds the compressor casing (28). Each variable stator vane (32) is connected to the control ring (38) by a respective one of a plurality of operating levers (40) and the control ring (38) is spaced from the compressor casing (28) by a clearance. A plurality of bimetallic strips (50) are arranged circumferentially and are positioned radially between the control ring (38) and the compressor casing (28) and the bimetallic strips (50) control the clearance between the control ring (38) and the compressor casing (28) whereby any error of the variable stator vane (32) angular position is reduced. Each bimetallic strip (50) extends radially outwardly from the compressor casing (28) towards the control ring (38). Each bimetallic strip (50) comprises a first metal strip (52) bonded to a second metal strip (54) and the first metal strip (52) has a different coefficient of thermal expansion than the second metal strip (54).