A method for directional drilling of a borehole in a formation, the method comprising the steps of: - providing a drill string having a drill bit at a downhole end thereof, the drill string comprising a central fluid passage extending along a longitudinal axis of the drill string for passing drilling fluid to the drill bit, a platform suspended in a set of bearings such that the platform is free to rotate about the axis of the drill string, which platform has position sensors fixed to it, and the drill bit comprising a plurality of nozzles (35, 38) for expelling the drilling fluid, each nozzle being arranged eccentrically with respect to the longitudinal axis; - introducing a bit steering assembly for steering the drill bit in the central fluid passage of the drill string; - rotating the drill string including the drill bit; - pumping drilling fluid through the central fluid passage of the drill string towards the drill bit; - the drilling fluid activating a first impeller of a first rotor section to rotate in a first direction with respect to the drill string; - the drilling fluid activating a second impeller of a second rotor section to rotate in a second direction opposite the first direction; and - adjusting a coupling to maintain an outlet member in a predetermined position with respect to the formation to drill a curved borehole section, wherein the position sensors can measure the rotational position of the outlet member; characterized in that the outlet member is a flow diverter connected to the first rotor section, and the first impeller is connected directly to the platform and the flow diverter, and the first rotor section is rotated in the first direction which is opposite to the rotation direction of the drill string, and wherein the coupling is adjusted between the first rotor section and the second rotor section whereby maintaining the first rotor section in said predetermined position with respect to the formation, comprising the step of diverting the drilling fluid in a predetermined direction relative to the formation using the flow diverter, wherein the step of diverting the drilling fluid comprises maintaining the first rotor section including the flow diverter in a substantially geo-stationary position with respect to the formation. - providing a drill string having a drill bit at a downhole end thereof, the drill string comprising a central fluid passage extending along a longitudinal axis of the drill string for passing drilling fluid to the drill bit, a platform suspended in a set of bearings such that the platform is free to rotate about the axis of the drill string, which platform has position sensors fixed to it, and the drill bit comprising a plurality of nozzles (35, 38) for expelling the drilling fluid, each nozzle being arranged eccentrically with respect to the longitudinal axis; - introducing a bit steering assembly for steering the drill bit in the central fluid passage of the drill string; - rotating the drill string including the drill bit; - pumping drilling fluid through the central fluid passage of the drill string towards the drill bit; - the drilling fluid activating a first impeller of a first rotor section to rotate in a first direction with respect to the drill string; - the drilling fluid activating a second impeller of a second rotor section to rotate in a second direction opposite the first direction; and - adjusting a coupling to maintain an outlet member in a predetermined position with respect to the formation to drill a curved borehole section, wherein the position sensors can measure the rotational position of the outlet member;