A transformer, with a primary side and a secondary side, comprising: a main pair of windings, comprising: a primary winding (970, 974) on the primary side; and a secondary winding on the secondary side, configured, in use, to be inductively coupled to the primary winding; a secondary circuit comprising the secondary winding, an output terminal and a secondary-side reference terminal, the output terminal connected to a first end of the secondary winding, the secondary-side reference terminal connected to a second end of the secondary winding; a primary-side auxiliary winding on the primary side, connected at a first end to a primary-side reference terminal, wherein in use the primary-side auxiliary winding is configured to be inductively coupled to the primary winding such that a first electric potential distribution is induced in the primary-side auxiliary winding; and a secondary-side auxiliary winding on the secondary side, the secondary-side auxiliary winding having a reference end, wherein the reference end is connected to a further reference terminal in the secondary circuit, wherein, in use, a first portion of the secondary-side auxiliary winding is configured to be inductively coupled to the primary winding such that a second electric potential distribution is induced in the secondary-side auxiliary winding; wherein the primary winding, secondary winding, primary-side auxiliary winding and the secondary-side auxiliary winding are coaxial; characterised in that: the primary-side auxiliary winding is physically radially located between (a) the main pair of windings; and (b) the secondary- side auxiliary winding; and a first portion of the secondary-side auxiliary winding is positioned radially adjacent to a shield-portion of the primary-side auxiliary winding such that the first electric potential distribution matches the second electric potential distribution: along the respective axial lengths of the first portion of the secondary-side auxiliary winding and the shield-portion of the primary-side auxiliary winding; and over a frequency range that is greater than a particular threshold frequency. a main pair of windings, comprising: a primary winding (970, 974) on the primary side; and a secondary winding on the secondary side, configured, in use, to be inductively coupled to the primary winding; a primary winding (970, 974) on the primary side; and a secondary winding on the secondary side, configured, in use, to be inductively coupled to the primary winding; a secondary circuit comprising the secondary winding, an output terminal and a secondary-side reference terminal, the output terminal connected to a first end of the secondary winding, the secondary-side reference terminal connected to a second end of the secondary winding; a primary-side auxiliary winding on the primary side, connected at a first end to a primary-side reference terminal, wherein in use the primary-side auxiliary winding is configured to be inductively coupled to the primary winding such that a first electric potential distribution is induced in the primary-side auxiliary winding; and a secondary-side auxiliary winding on the secondary side, the secondary-side auxiliary winding having a reference end, wherein the reference end is connected to a further reference terminal in the secondary circuit, wherein, in use, a first portion of the secondary-side auxiliary winding is configured to be inductively coupled to the primary winding such that a second electric potential distribution is induced in the secondary-side auxiliary winding; wherein the primary winding, secondary winding, primary-side auxiliary winding and the secondary-side auxiliary winding are coaxial; characterised in that: the primary-side auxiliary winding is physically radially located between (a) the main pair of windings; and (b) the secondary- side auxiliary winding; and a first portion of the secondary-side auxiliary winding is positioned radially adjacent to a shield-portion of the primary-side auxiliary winding such that the first electric potential distribution matches the second electric potential distribution: along the respective axial lengths of the first portion of the secondary-side auxiliary winding and the shield-portion of the primary-side auxiliary winding; and over a frequency range that is greater than a particular threshold frequency. the primary-side auxiliary winding is physically radially located between (a) the main pair of windings; and (b) the secondary- side auxiliary winding; and a first portion of the secondary-side auxiliary winding is positioned radially adjacent to a shield-portion of the primary-side auxiliary winding such that the first electric potential distribution matches the second electric potential distribution: along the respective axial lengths of the first portion of the secondary-side auxiliary winding and the shield-portion of the primary-side auxiliary winding; and over a frequency range that is greater than a particular threshold frequency. along the respective axial lengths of the first portion of the secondary-side auxiliary winding and the shield-portion of the primary-side auxiliary winding; and over a frequency range that is greater than a particular threshold frequency.