During the Second World War RAF aircraft that were secret or carrying secret equipment had '' \ / G '' ( for `` Guard '' ) appended to the serial , denoting that the aircraft was to have an armed guard at all times while on the ground , e.g. , LZ548\/G-the prototype de Havilland Vampire jet fighter , or ML926\/G-a de Havilland Mosquito XVI experimentally fitted with H2S radar .
During the Second World War RAF aircraft carrying secret equipment or that were in themselves secret had '' \ / G '' added to the end of the serial , the `` G '' signifying `` Guard '' , denoting that the aircraft was to have an armed guard at all times while on the ground , e.g. , LZ548\/G-the prototype de Havilland Vampire jet fighter , or ML926\/G-a de Havilland Mosquito XVI experimentally fitted with H2S radar .