A system for positioning an intermediate head clamp on a subject for medical interventions thereon, comprising: - a superior positioning cap configured for placement on a head of the subject, - an intermediate head clamp, wherein the intermediate clamp comprises a main body, a holding space at least partially surrounded by the main body dimensioned to receive the head of the subject, a plurality of clamps (390, a-d) each configured for advancement into the holding space or withdrawal therefrom and for contacting the part of the head of the subject, wherein deployment of the plurality of clamps (390, a-d) fixes a pose of the main body relative to the head of the subject, - an inferior positioning support comprising a main body configured for placement around the head of the subject in a region coinciding with the forehead, and a plurality of locating bodies (460, 470, 480) each for locating in and engaging with a bodily recess of the subject's head and each locating body (460, 470, 480) being attached in adjustable and fixable in positional relation to the main body of the inferior positioning support, wherein the plurality of locating bodies (460, 470, 480) adjusts the pose of the inferior positioning support and of an axis of reference of the inferior positioning support in relation to the head, characterised in that: - the superior positioning cap has a domed receiving space for receiving a part of the head of the subject, wherein the superior positioning cap is provided with a plurality of adjustable protrusions (260, a, b, c, d, e), each configured for controlled advancement into the domed receiving space or withdrawal therefrom and for contacting a part of the head of the subject, wherein the plurality of adjustable protrusions (260, a, b, c, d, e) adjusts a pose of the superior positioning cap and of an axis of reference of the superior positioning cap in relation to the head, and - the superior positioning cap and inferior positioning support are configured to flank and each engage with the intermediate head clamp such that the axes of reference (250, 450) of the superior positioning cap and of the inferior positioning support are co-axial, and intermediate head clamp is rotatable around an axis of rotation co-axial with the axes of reference (250, 450) of the superior positioning cap and of the inferior positioning support. - a superior positioning cap configured for placement on a head of the subject, - an intermediate head clamp, wherein the intermediate clamp comprises a main body, a holding space at least partially surrounded by the main body dimensioned to receive the head of the subject, a plurality of clamps (390, a-d) each configured for advancement into the holding space or withdrawal therefrom and for contacting the part of the head of the subject, wherein deployment of the plurality of clamps (390, a-d) fixes a pose of the main body relative to the head of the subject, - an inferior positioning support comprising a main body configured for placement around the head of the subject in a region coinciding with the forehead, and a plurality of locating bodies (460, 470, 480) each for locating in and engaging with a bodily recess of the subject's head and each locating body (460, 470, 480) being attached in adjustable and fixable in positional relation to the main body of the inferior positioning support, wherein the plurality of locating bodies (460, 470, 480) adjusts the pose of the inferior positioning support and of an axis of reference of the inferior positioning support in relation to the head, - the superior positioning cap has a domed receiving space for receiving a part of the head of the subject, wherein the superior positioning cap is provided with a plurality of adjustable protrusions (260, a, b, c, d, e), each configured for controlled advancement into the domed receiving space or withdrawal therefrom and for contacting a part of the head of the subject, wherein the plurality of adjustable protrusions (260, a, b, c, d, e) adjusts a pose of the superior positioning cap and of an axis of reference of the superior positioning cap in relation to the head, and - the superior positioning cap and inferior positioning support are configured to flank and each engage with the intermediate head clamp such that the axes of reference (250, 450) of the superior positioning cap and of the inferior positioning support are co-axial, and intermediate head clamp is rotatable around an axis of rotation co-axial with the axes of reference (250, 450) of the superior positioning cap and of the inferior positioning support.