Abstract: A bending mechanism for flexible waveguide uses a combination of an elongate arm (1), two short bracket arms (3 & 7) and a gear train (5, 11, 13 & 9) linking the bracket arms to bend a flexible waveguide (24) over a range of positions. The bend is formed to the shape of a circular arc the radius of which varies with the position. Each short bracket arm is pivotally connected (15 & 17) to a respective end of the elongate arm and to a respective one of the waveguide's two end flanges (23 & 25). Each bracket arm contains a gear that rotates with the respective bracket arm about the bracket arm's pivot; and an even number of gears interlinks those gears whereby pivotal movement of one of the flanges in a clockwise direction produces an effective relative pivotal movement of the other flange.