A split-core current measurement device comprising: a first arm including a first magnetic core portion (6a, 6b); a second arm including a second magnetic core portion; a first sensing element sensitive to changes in magnetic field; the first and second magnetic core portions being shaped so that, when the first and second arms of the measurement device are in a closed configuration, the first and second magnetic core portions cooperate to form a substantially complete magnetic circuit configured to act as a flux guide when the measurement device surrounds a current carrying conductor; wherein the first magnetic core portion includes a first non-magnetic core discontinuity; and wherein the first magnetic core portion defines a first internal cavity within which the first sensing element is contained such that at least a portion of the first sensing element is located in the first non-magnetic core discontinuity, the first magnetic core portion comprises separate first and second sectors (6a, 6b), wherein a first end of the first sector and a first end of the second sector are separated by a non-magnetic clearance due to the presence of the first non-magnetic core discontinuity, and characterised in that the clearance between the first end of the first sector and the first end of the second sector is less than i) a clearance between the first end of the first sector and a first magnetic shield portion of the first arm, and/or ii) a clearance between the first end of the second sector and the first magnetic shield portion, to thereby reduce flux leakage between the first magnetic core portion and the first magnetic shield portion. a first arm including a first magnetic core portion (6a, 6b); a second arm including a second magnetic core portion; a first sensing element sensitive to changes in magnetic field; the first and second magnetic core portions being shaped so that, when the first and second arms of the measurement device are in a closed configuration, the first and second magnetic core portions cooperate to form a substantially complete magnetic circuit configured to act as a flux guide when the measurement device surrounds a current carrying conductor; wherein the first magnetic core portion includes a first non-magnetic core discontinuity; and wherein the first magnetic core portion defines a first internal cavity within which the first sensing element is contained such that at least a portion of the first sensing element is located in the first non-magnetic core discontinuity, the first magnetic core portion comprises separate first and second sectors (6a, 6b), wherein a first end of the first sector and a first end of the second sector are separated by a non-magnetic clearance due to the presence of the first non-magnetic core discontinuity, and characterised in that the clearance between the first end of the first sector and the first end of the second sector is less than i) a clearance between the first end of the first sector and a first magnetic shield portion of the first arm, and/or ii) a clearance between the first end of the second sector and the first magnetic shield portion, to thereby reduce flux leakage between the first magnetic core portion and the first magnetic shield portion.