An oil insulated rotational drive comprising an oil filled cavity defined by an electrically insulating cavity wall, the cavity wall comprising first and second spaced apart end faces and a side wall extending therebetween, each end face having an aperture extending therethrough; a first rotational drive arm extending through the aperture in the first end face; a second rotational drive arm extending through the aperture in the second end face; the two arms being co-axial and arranged to rotate about a rotational axis extending along the length of the rotational drive arms; the two rotational drive arms being connected to an electrically insulating drive body arranged within the cavity and adapted to rotate about the rotational axis.