An electrical isolator includes a body defining an aperture therethrough, a first electrical contact disposed at a first end of the aperture, a second electrical contact movably disposed at a second end of the aperture, the second contact configured to be operatively movable through the aperture to electrically connect to, or disconnect from, the first contact and at least two concave electrical field control screens fixed to the body at respective ends of, and about, the aperture such that the screens lie transverse to the aperture and an open-end of each concave screen is directed towards the other.