Chief Mouser to the Cabinet Office
Chief Mouser to the Cabinet Office is the title of the official resident cat at 10 Downing Street, the residence and office of the prime minister of the United Kingdom in London. There has been a resident cat in the British government employed as a mouser and pet since the 16th century, although modern records date only to the 1920s.
Source: Wikipedia — Chief Mouser to the Cabinet Office (CC BY-SA 4.0)