A surgical system comprising: means for tracking a plurality of elements (211, 212), each element being mounted, in use, on a unique part of a human hand, to obtain a plurality of locations of the plurality of elements (211, 212); means for selecting a hand gesture pose from a plurality of known hand gesture poses (300A-300D) based on the plurality of locations, each hand gesture pose of the plurality of known hand gesture poses (300A-300D), other than a hand gesture pose used in each of a plurality of known hand gesture trajectories, being assigned to one of a first plurality of system modes of operation, wherein modes of operation of the surgical system comprise the first plurality of system modes of operation; means for determining whether the selected hand gesture pose is the hand gesture pose used in each of the plurality of known hand gesture trajectories; means for selecting a hand gesture trajectory from the plurality of known hand gesture trajectories (400A, 400B) based on the plurality of locations, if the means for determining finds that the selected hand gesture pose is the hand gesture pose used in each of the plurality of known hand gesture trajectories, each hand gesture trajectory of the plurality of known hand gesture trajectories (400A, 400B) being assigned to one of a second plurality of system modes of operation, wherein the modes of operation of the surgical system further comprises the second plurality of system modes; and means for changing a mode of operation of the surgical system, the means for changing being configured to change the mode of operation of the surgical system to one of the first plurality of system modes of operation based on the selected hand gesture pose, if the selected hand gesture pose is other than the hand gesture pose used in each of the plurality of known hand gesture trajectories; and the means for changing being configured to change the mode of operation of the surgical system to one of the second plurality of system modes of operation based on the selected hand gesture trajectory, if the selected hand gesture pose is the hand gesture pose used in each of the plurality of known hand gesture trajectories. means for tracking a plurality of elements (211, 212), each element being mounted, in use, on a unique part of a human hand, to obtain a plurality of locations of the plurality of elements (211, 212); means for selecting a hand gesture pose from a plurality of known hand gesture poses (300A-300D) based on the plurality of locations, each hand gesture pose of the plurality of known hand gesture poses (300A-300D), other than a hand gesture pose used in each of a plurality of known hand gesture trajectories, being assigned to one of a first plurality of system modes of operation, wherein modes of operation of the surgical system comprise the first plurality of system modes of operation; means for determining whether the selected hand gesture pose is the hand gesture pose used in each of the plurality of known hand gesture trajectories; means for selecting a hand gesture trajectory from the plurality of known hand gesture trajectories (400A, 400B) based on the plurality of locations, if the means for determining finds that the selected hand gesture pose is the hand gesture pose used in each of the plurality of known hand gesture trajectories, each hand gesture trajectory of the plurality of known hand gesture trajectories (400A, 400B) being assigned to one of a second plurality of system modes of operation, wherein the modes of operation of the surgical system further comprises the second plurality of system modes; and means for changing a mode of operation of the surgical system, the means for changing being configured to change the mode of operation of the surgical system to one of the first plurality of system modes of operation based on the selected hand gesture pose, if the selected hand gesture pose is other than the hand gesture pose used in each of the plurality of known hand gesture trajectories; and the means for changing being configured to change the mode of operation of the surgical system to one of the second plurality of system modes of operation based on the selected hand gesture trajectory, if the selected hand gesture pose is the hand gesture pose used in each of the plurality of known hand gesture trajectories.