What is the title of the official resident cat of the Prime Minister of the UK at 10 Downing Street?

The Chief Mouser to the Cabinet Office is the title of the official resident cat of the Prime Minister of the United Kingdom at 10 Downing Street. Only three cats, Humphrey, Sybil and Larry, have been given the title officially. Other cats have been given this title as a nickname.

There has been a resident cat in the English government employed as a mouser and pet since the 1500s but modern records date only to the 1920s. The cats do not always belong to the Prime Minister in residence. Only rarely do they serve for exactly the same time as a Prime Minister. The cat with the longest known time at Downing Street is Wilberforce. He served for eighteen years under Edward Heath, Harold Wilson, Jim Callaghan, and Margaret Thatcher.

Sybil the cat served from 2007 till 2009. It was reported that Sybil did not like living in London. In 2009 she went back to Scotland to live with a friend until she died. The position was left vacant. In January 2011, rats were seen in Downing Street, "scurrying across the steps of Number 10 Downing Street during a TV news report", as reported by Independent Television News. On 14 February 2011 a cat named "Larry" had been brought in to get rid of the rodents. He took the position of the Chief Mouser to the Cabinet Office.

Larry the cat has a Twitter account. He introduces himself as follows, "Chief Mouser to the Cabinet Office. I'm a 12 year old tabby, in position longer than the leader of any UK political party."