For centuries, Britain’s government has battled an unrelenting enemy that multiplies rapidly and invades the corridors of power of the state. No, not politicians, but armies of rodents. The solution? Cats — stealthy, ruthless, and unquestionably adorable.

Since Henry VIII’s reign, cats have patrolled Whitehall, keeping rodents at bay, and making sure meals and naps are never missed. Henry’s chancellor, Cardinal Thomas Wolsey, brought cats to judicial meetings and these early feline companions paved the way for today’s Chief Mousers.

Official records of Chief Mousers only date back to 1924, and it was not until 1929 that the Treasury supported the “Chief Mouser” position, approving a daily penny for an “efficient cat” to combat rodents in Downing Street. Whitehall is a complex of central UK government ministerial and non-ministerial departments, including the Cabinet Office, Ministry of Defence, and Foreign, Commonwealth and Development Office, and some of these also employ their own Chief Mousers and some are mentioned here.

At the Cabinet Office at 10 Downing Street , Rufus of England, nicknamed “Treasury Bill,” served six years (1924-30) as Chief Mouser under Prime Minister Ramsey MacDonald. He was followed by ​Peter I (1929-1946), who served under five prime ministers: MacDonald, Baldwin, Chamberlain, Churchill, and Attlee.

His successor was Bob, nicknamed “Munich Mouser,” named by Winston Churchill after the Munich Agreement. He served in the role from 1937 to 1943, during the tenures of Neville Chamberlain and Churchill’s first term. ​In 1940, a cat named Nelson was brought in to help Bob, the Munich Mouser, during Winston Churchill’s first term. The exact duration of Nelson’s service is unknown. Churchill, known for his fondness for cats, also kept them as pets in his personal home.

​Peter II, a black kitten, took up the role from 1946–47, but never recovered after being injured in a car accident in Whitehall. ​His successor Peter III, served from 1947 to 1964, under five Prime Ministers: Attlee, Churchill, Eden, Macmillan, and Douglas-Hume, making him the longest-serving cat to date (17 years). He achieved fame after a national television appearance and was succeeded by Peta, the first female Chief Mouser. She served from 1964 to 1976 under Alec Douglas-Hume, Harold Wilson, and Edward Heath, succeeding Peter III and preceding Wilberforce, an adoptee from the RSPCA.

​Wilberforce served as unofficial Chief Mouser at Number 10 from 1973 to 1986. During these years, he served under four prime ministers: Edward Heath (1970–1974), Harold Wilson (1974–1976), James Callaghan (1976–1979), and Margaret Thatcher (1979–1990). He was known for waiting at the Number 10 door until a police officer knocked to let him in.

​From 1989 to 1997, Humphrey, another adopted stray, had the misfortune to serve as honorary Chief Mouser to Prime Ministers Thatcher, Major, and Blair. The Downing Street mice were allowed to run riot until 2007. Chancellor Alistair Darling at 11 Downing Street, brought Sybil, a female cat named after Sybil Fawlty from the TV comedy series Fawlty Towers, to restore order out of chaos. Her tenure lasted until 2009.

It was not until 2011 that Prime Minister David Cameron responded to the growing rodent problems at Downing Street. He adopted a stray tabby named Larry from Battersea Dogs and Cats Home to manage the situation at Number 10. Larry became the first cat to be given the official title, “First Mouser to the Cabinet Office.”

​In 2012, as ministerial changes occurred in Downing Street, Chancellor George Osborne’s cat, Freya, shared rodent-control duties alongside Larry, despite having survived a car accident. This led to a rivalry between the two, resulting in frequent clashes over territory.  But Freya’s departure in 2014 left Larry the undisputed Chief Mouser.​ Cameron confirmed in his final Prime Minister’s Questions on 13 July 2016 that Larry would remain Chief Mouser after he left office.

Meanwhile, in 2016, the Foreign & Commonwealth Office in King Charles Street appointed Palmerston, a black-and-white tuxedo cat, as their Chief Mouser, who regularly clashed with Larry over territory. Palmerston served for four years, from 2016 until his retirement in 2020, but briefly resumed duties in 2025 in Bermuda, accompanying his owner, Andrew Murdoch, the newly appointed Governor of Bermuda.

In October 2022, after outlasting Palmerston, Larry heroically chased away a fox nearly twice his size from outside 10 Downing Street. Even more heroically, he went on to serve under Prime Ministers Theresa May, Boris Johnson, Liz Truss, and Rishi Sunak, welcoming Sir Keir Starmer into Number 10, whom he is also likely to outlast.

Larry did not always take to male foreign dignitaries visiting number 10, but during President Obama’s 2011 visit to the UK the two appeared to strike up a rapport which received major US media coverage.

​​Over at HM Treasury, 1 Horse Guards Road, Gladstone, a black domestic short-haired cat born around December 2014 became the Chief Mouser in late June 2016, aged 18 months. Named after former Chancellor and Prime Minister William Gladstone, he was responsible for rodent control at the Treasury until his retirement in 2019.

On June 4, 2019, during a photo shoot outside No. 10, Larry upstaged Prime Minister Theresa May, her husband, Philip May, and President Donald Trump and First Lady Melania Trump during their state visit. An Official White House photograph by Andrea Hanks captures Larry seated on the left side window ledge, casually watching the photo shoot take place from a safe distance away from President Trump.

​After PM Sunak’s surprise May 2024 general election announcement in the rain, Larry was seen patiently watching from the shelter of Number 10’s front door as Sunak got soaked while making his announcement.

​In the modern world full of technological marvels and wonders, it seems quaintly ironic that the most effective means of keeping the rodents of Whitehall under control is still our feline friends!