A terminal unit comprising: a terminal unit body; a first terminal located adjacent a first opening in the terminal unit body for connection of a first conductor passing through the first opening; a second terminal located adjacent a second opening in the terminal unit body for connection of a second conductor passing through the second opening, the first terminal and the second terminal being located at opposite ends of the terminal unit body; a link opening arranged between the first terminal and the second terminal, a first terminal conductor extending internally of the terminal unit body from the first terminal to a first link connection point at the link opening, a second terminal conductor extending internally of the terminal unit body from the second terminal to a second link connection point at the link opening, the first and second link connection points (303, 303) being accessible via the link opening, and a removable link comprising a link conductor and a link handle, the removable link being removably insertable into the link opening in a normal orientation and in a reverse orientation, wherein the first link connection point and the second link connection point sit side by side within the link opening separated by an insulating wall such that they cannot be connected by a straight conductor, wherein, in the normal orientation, the link conductor electrically connects the first link connection point and the second link connection point to electrically connect the first terminal to the second terminal and the link handle projects from the link opening, wherein, in the reverse orientation, the link handle is inserted into the link opening without connecting the first link connection point to the second link connection point and the link conductor projects from the link opening, and wherein the removable link includes a shroud which at least partially shrouds the link conductor, and the shroud has a different colour to the link handle such that the different colour is visible when the removable link is inserted into the link opening in the reverse orientation. a terminal unit body; a first terminal located adjacent a first opening in the terminal unit body for connection of a first conductor passing through the first opening; a second terminal located adjacent a second opening in the terminal unit body for connection of a second conductor passing through the second opening, the first terminal and the second terminal being located at opposite ends of the terminal unit body; a link opening arranged between the first terminal and the second terminal, a first terminal conductor extending internally of the terminal unit body from the first terminal to a first link connection point at the link opening, a second terminal conductor extending internally of the terminal unit body from the second terminal to a second link connection point at the link opening, the first and second link connection points (303, 303) being accessible via the link opening, and a removable link comprising a link conductor and a link handle, the removable link being removably insertable into the link opening in a normal orientation and in a reverse orientation, wherein the first link connection point and the second link connection point sit side by side within the link opening separated by an insulating wall such that they cannot be connected by a straight conductor, wherein, in the normal orientation, the link conductor electrically connects the first link connection point and the second link connection point to electrically connect the first terminal to the second terminal and the link handle projects from the link opening, wherein, in the reverse orientation, the link handle is inserted into the link opening without connecting the first link connection point to the second link connection point and the link conductor projects from the link opening, and wherein the removable link includes a shroud which at least partially shrouds the link conductor, and the shroud has a different colour to the link handle such that the different colour is visible when the removable link is inserted into the link opening in the reverse orientation.