A gas turbine engine having an electrical harness for transferring electrical signals around the engine, the electrical harness comprising an electrical raft assembly having an electrical raft comprising: a rigid material having multiple electrical conductors embedded therein so as to be surrounded by and fixed in position by the rigid material; and an electrically conductive screen layer, wherein: the gas turbine engine is a turbofan engine comprising a bypass flow duct formed between an engine core and an engine fan casing; the gas turbine engine comprises a mounting structure, the mounting structure being a part of a fan case, a core case or a bifurcation splitter that radially crosses the bypass duct; the electrical raft is an elongate member having an upper major surface and a lower major surface separated by a raft thickness; at least some of the electrical conductors are provided in a flexible printed circuit as electrically conductive tracks in a flexible substrate; the electrically conductive screen layer is at least partially embedded in the rigid material and is substantially parallel to at least one of the upper and lower major surfaces of the electrical raft; the electrical raft assembly further comprises a mounting fixture for attaching the electrical raft assembly to the mounting structure the gas turbine engine; and the mounting fixture is in electrical contact with the electrically conductive screen layer and is mechanically and electrically connected to the mounting structure, thereby electrically connecting the electrically conductive screen layer to the rest of the gas turbine engine. a rigid material having multiple electrical conductors embedded therein so as to be surrounded by and fixed in position by the rigid material; and an electrically conductive screen layer, wherein: the gas turbine engine is a turbofan engine comprising a bypass flow duct formed between an engine core and an engine fan casing; the gas turbine engine comprises a mounting structure, the mounting structure being a part of a fan case, a core case or a bifurcation splitter that radially crosses the bypass duct; the electrical raft is an elongate member having an upper major surface and a lower major surface separated by a raft thickness; at least some of the electrical conductors are provided in a flexible printed circuit as electrically conductive tracks in a flexible substrate; the electrically conductive screen layer is at least partially embedded in the rigid material and is substantially parallel to at least one of the upper and lower major surfaces of the electrical raft; the electrical raft assembly further comprises a mounting fixture for attaching the electrical raft assembly to the mounting structure the gas turbine engine; and the mounting fixture is in electrical contact with the electrically conductive screen layer and is mechanically and electrically connected to the mounting structure, thereby electrically connecting the electrically conductive screen layer to the rest of the gas turbine engine. the gas turbine engine is a turbofan engine comprising a bypass flow duct formed between an engine core and an engine fan casing; the gas turbine engine comprises a mounting structure, the mounting structure being a part of a fan case, a core case or a bifurcation splitter that radially crosses the bypass duct; the electrical raft is an elongate member having an upper major surface and a lower major surface separated by a raft thickness; at least some of the electrical conductors are provided in a flexible printed circuit as electrically conductive tracks in a flexible substrate; the electrically conductive screen layer is at least partially embedded in the rigid material and is substantially parallel to at least one of the upper and lower major surfaces of the electrical raft; the electrical raft assembly further comprises a mounting fixture for attaching the electrical raft assembly to the mounting structure the gas turbine engine; and the mounting fixture is in electrical contact with the electrically conductive screen layer and is mechanically and electrically connected to the mounting structure, thereby electrically connecting the electrically conductive screen layer to the rest of the gas turbine engine.