Operating mechanism for M.V. earthing switch, respectively medium voltage earthing switch, comprising: - an operating disk rotating about a main axis between a first angular position and a second angular position that correspond, respectively, to an opening condition and to a closing condition of said earthing switch; - a connecting assembly which connects operatively said operating disk to said earthing switch; - an operating lever for rotating said disk from said first angular position to said second angular position according to a closing movement and from second angular position to said first angular position according to an opening movement, wherein said connecting assembly transforms said closing movement and said opening movement of said disk, respectively, in a closing movement and in an opening movement of said earthing switch, wherein said operating mechanism comprises an interlock assembly that prevents a re-closing movement of said disk when, starting from said second angular position and according to said opening movement, said disk reaches a pre-established angle (α), wherein said interlock assembly comprises a first sub-assembly integral with said disk and a second sub-assembly which interacts with said first sub-assembly, said second sub-assembly being mounted on a fixed frame, wherein said first sub-assembly comprises a first element integral with said disk and said second sub-assembly comprises a first element hinged to said frame and rotating under the action of at least one first spring element (51A, 51B), wherein in a locking position said first rotating element cooperates with said first element of said first sub-assembly to prevent said re-closing movement, wherein said first sub-assembly comprises a second element integral with said disk, characterised in that during the rotation of said disk according to said opening movement, said second element moves said first rotating element from said locking position to an unlocking position loading said at least one first spring element (51A, 51B), and wherein said second sub-assembly comprises a second rotating element hinged to said frame and subjected to the action of at least one second spring element, said second rotating element locking said first rotating element when the latter reaches said unlocking position. - an operating disk rotating about a main axis between a first angular position and a second angular position that correspond, respectively, to an opening condition and to a closing condition of said earthing switch; - a connecting assembly which connects operatively said operating disk to said earthing switch; - an operating lever for rotating said disk from said first angular position to said second angular position according to a closing movement and from second angular position to said first angular position according to an opening movement, wherein said connecting assembly transforms said closing movement and said opening movement of said disk, respectively, in a closing movement and in an opening movement of said earthing switch, said operating mechanism comprises an interlock assembly that prevents a re-closing movement of said disk when, starting from said second angular position and according to said opening movement, said disk reaches a pre-established angle (α), wherein said interlock assembly comprises a first sub-assembly integral with said disk and a second sub-assembly which interacts with said first sub-assembly, said second sub-assembly being mounted on a fixed frame, wherein said first sub-assembly comprises a first element integral with said disk and said second sub-assembly comprises a first element hinged to said frame and rotating under the action of at least one first spring element (51A, 51B), wherein in a locking position said first rotating element cooperates with said first element of said first sub-assembly to prevent said re-closing movement, wherein said first sub-assembly comprises a second element integral with said disk, characterised in that during the rotation of said disk according to said opening movement, said second element moves said first rotating element from said locking position to an unlocking position loading said at least one first spring element (51A, 51B), and wherein said second sub-assembly comprises a second rotating element hinged to said frame and subjected to the action of at least one second spring element, said second rotating element locking said first rotating element when the latter reaches said unlocking position.