Our photo outside 10 Downing Street, taken from undated newsreel footage but probably around the time of the outbreak of war, may show the Mouser, but we're unable to confirm that; another possibility is that it's Nelson, one of Churchill's own cats, who was black and did spend some time at No. At some point there was also Emily of the Home Office, apparently picked up in the street by a charwoman, but who became so wise and engaging that she always sat in at conferences with the Home Secretary.
Later there were several Home Office cats called Peter, or Peta (see separate page).
We haven't been able to find out his real name; apparently he was nicknamed the Munich Mouser, somewhat disrespectfully, by Churchill as he was a holdover from former Prime Minister Chamberlain's administration.
He was found by a member of the Cabinet Office staff (70 Whitehall, next to the prime minister's London residence of No. He was about a year old and, following a ballot among staff, was named after Sir Humphrey Appleby in the very popular BBC television comedy show Yes, Minister, and given the official title of Mouser to the Cabinet Office; his food was paid for by the departmental budget.
10 Downing Street) in October 1989, late in Margaret Thatcher's prime ministership, and remained throughout John Major's term in office (one of the few inhabitants of No. The cost of £100 a year was said to appeal to Mrs Thatcher because it was much cheaper than hiring a pest-control contractor (the previous one charged £4,000 a year and was said never to have caught a mouse! Humphrey's eight years in the corridors of power saw him mingling with the great and the good (and others), which he did with aplomb and the natural dignity of his kind; he was described as a laid-back and relaxed cat, which was probably just as well. 11, the residence of the Chancellor of the Exchequer, and the adjacent Cabinet Office.
Even before that Frilly was resident cat at the British War Office in around 1909 and was on the official payroll.
When he died the employees had a collection to pay for him to be stuffed and preserved for posterity, and in this guise he appeared at the Imperial War Museum's Animals' War exhibition in 2007.
And coming right up to contemporary times, it was announced in July 2016 that a new mouser had been appointed for the Treasury.