A tying mechanism comprising a bill hook (82), twine holding means (86, 220) for holding strands of twines, a cutting arm (88) adapted for cutting twines between the bill hook and the twine holding means whilst moving between a rest position and an extended position, a drive means (76,96,98,100,101,110,112) adapted to make the bill hook perform at least a first full rotation and a second full rotation and to move the cutting arm from the rest position to the extended position and back during a full operation cycle to form respectively a first and a second consecutive knot wherein the tying mechanism further comprises a tension regulating mechanism (200, 221, 222, 222', 240, 250) which is able to provide and regulate the tension exerted to the twine holding means (86, 220) during the operation of the tying mechanism.
