The invention provides a fluid flow control valve (1) comprising a cylindrical inlet chamber (2) having a fluid inlet aperture (3) and a coaxial waisted cylindrical outlet chamber (4) having a fluid outlet aperture (5), said inlet chamber containing a coaxial cylindrical cage (6) opening into said outlet chamber and said cage having in its cylinder wall at least one valve aperture (7) to allow fluid to pass from said fluid inlet aperture into said outlet chamber, said control valve further comprising a coaxial cylindrical plug (10) movable axially relative to said cage to close and open said valve aperture and a valve actuator (9, 11, 12, 13) operable to move said plug or cage relative to each other whereby to close or open said valve aperture, wherein said valve aperture is arranged to provide fluid exiting said cage from said inlet chamber with a velocity component tangential to the cylindrical axis (31) of said cage.