A method for monitoring a torsional state of an electric cable (1; 36) having a central longitudinal axis, the method comprising - providing an electric cable including a torsion sensor longitudinally extending along the cable, said torsion sensor including a single-mode optical fibre arranged substantially along the central longitudinal axis of the cable (1; 36), characterised in that the cable comprises at least three longitudinal structural elements (2, 3, 7), at least one of the longitudinal structural elements (2, 3, 7) being an electrically conductive core, wherein the torsion sensor is mechanically coupled with at least one of the longitudinal structural elements (2, 3, 7), and measuring a torsional state of the single-mode optical fibre by polarisation-sensitive optical reflectometry, said measuring comprising: - injecting a plurality of probe optical signals having distinct input polarisation states into an end of the single-mode optical fibre; - detecting a plurality of backscattered optical signals, each of the plurality of backscattered optical signals having an output state of polarisation; - measuring the output states of polarisation of the backscattered optical signals; - calculating a birefringence angle function as a function of longitudinal position of the single-mode optical fibre from the measured output states of polarisation, and - calculating a rotational angle function of the single-mode optical fibre from the birefringence angle function as a function of the longitudinal position in the single-mode optical fibre, and - associating a torsional state of the single-mode optical fibre with the calculated rotational angle function, wherein the method comprises associating the torsional state of the cable (1; 36) along the central longitudinal axis with the measured torsional state of the single-mode optical fibre. - providing an electric cable including a torsion sensor longitudinally extending along the cable, said torsion sensor including a single-mode optical fibre arranged substantially along the central longitudinal axis of the cable (1; 36), characterised in that the cable comprises at least three longitudinal structural elements (2, 3, 7), at least one of the longitudinal structural elements (2, 3, 7) being an electrically conductive core, wherein the torsion sensor is mechanically coupled with at least one of the longitudinal structural elements (2, 3, 7), and - injecting a plurality of probe optical signals having distinct input polarisation states into an end of the single-mode optical fibre; - detecting a plurality of backscattered optical signals, each of the plurality of backscattered optical signals having an output state of polarisation; - measuring the output states of polarisation of the backscattered optical signals; - calculating a birefringence angle function as a function of longitudinal position of the single-mode optical fibre from the measured output states of polarisation, and - calculating a rotational angle function of the single-mode optical fibre from the birefringence angle function as a function of the longitudinal position in the single-mode optical fibre, and - associating a torsional state of the single-mode optical fibre with the calculated rotational angle function,