There’s a ‘cat-astrophe’ brewing on Downing Street

But the former prosecutor has another issue troubling him: How to handle Larry the Cat.

Everyone knows the real power at 10 Downing St. is Larry, a tabby who has ruled the roost since 2011. He was brought in by former Prime Minister David Cameron’s family as a rescue to help rid the offices of unwanted rodents.

Larry, officially the Chief Mouser to the Cabinet Office, has now outlasted five prime ministers—and their pets. A British icon, he has his own X account, with 900K followers. He is so well known that Downing St. has even reportedly made plans for how to break the news of his eventual death (Larry is 17).

Which brings us back to Starmer, the sixth British leader of Larry’s tenure. Starmer, his wife, Victoria, and two teenage children moved into 10 Downing in July after a sweeping election victory. But another family member also moved in: JoJo, a male ginger cat.

JoJo has yet to meet Larry, and the family is working out how to engineer an encounter that doesn’t end in flying fur, according to sources familiar with the matter. The Daily Mail tabloid warned of a “cat-astrophe" if the meeting goes wrong.

‘It’s Larry’s domain’

Larry, like many cats, doesn’t always take well to newcomers, especially those on four legs. Larry had “heated exchanges" with Nova, the Labrador owned by former Prime Minister Rishi Sunak’s family. Nova came out on the losing end, Sunak’s wife Akshata Murty told reporters. Larry also has a history with Boris Johnson’s rescue dog Dilyn, a Jack Russel.

“Larry, in my view, is a bit of a thug. I say this because our dog Dilyn went a few times to Larry’s lair, and Larry being out at the time Dilyn decided—entirely naturally and reasonably—to eat his food. The reprisals were terrible," Johnson wrote in a newspaper column, dubbing Larry “catzilla."

Police had to break up Larry’s fisticuffs with Freya, former chancellor George Osborne’s cat. And Larry tussled with Palmerston, a feline that performed similar duties—moral support for staff and perhaps catching the occasional mouse—at the nearby British Foreign and Commonwealth Office. Palmerston, who once had his ear damaged during an encounter with Larry, retired to the countryside in 2020.

“I think Larry is quite territorial," says Justin Ng, a freelance photographer who has taken pictures of Larry outside No. 10 since 2014. “It’s Larry’s domain, he’ll feel he’s been threatened with another cat coming in." He and Palmerston eventually developed a wary understanding and would often sleep next to each other, says Ng.

Far from being spooked, the Starmers have doubled down, and this week bought a new Siberian kitten, the prime minister told BBC radio.

For Larry, this might be the lesser of two evils: the Starmer teens originally wanted a German shepherd, but relented after a summer of negotiations, he said.

For now, JoJo and the new kitten are largely confined to the family’s living quarters and Larry gets the run of the rest of the building, including coming in and out of the famous black-door entrance, usually thanks to a guard who knocks politely when Larry wants back in.

Starmer said one obstacle to freedom of movement for JoJo and the kitten was how to install a cat flap on the residence’s bombproof door, which he said was turning out to be a challenge.

The animal-loving British are full of advice. Cats Protection, a charity, said the Starmers are right to take time introducing the cats. They suggested the felines get acquainted through scent before meeting face-to-face.

“Do this by using a small flannel or blanket to wipe over each cat, and then place near the other cat," the charity suggested. Country Living magazine published a step-by-step guide for the first family.

As far as the kitten, Cats Protection said an older cat like Larry might get a bit grumpy if the kitten is too playful and energetic. Give Larry his space.

Larry’s antics provide great fodder for a British press corps who gather outside Downing St. for major announcements. He has been filmed attacking a pigeon and chasing off a much larger fox. This past week, he was interviewed by a Japanese TV crew.

He likes the attention and will approach the media to sniff around bags and get a quick cuddle, reporters say. The media often try to get Larry in their frames because he plays so well with the public. “I think a lot of people need that reassurance that Larry’s around to make their day better," says Ng.

Soft skills

Larry takes to some prime ministers better than others. Theresa May was apparently not a cat person, and there were unconfirmed reports that Larry peed in her shoes, Ng says. Boris Johnson might not have been a fan, but he made sure to pick up Larry several times for posed pictures.

Larry acts as a litmus test for politicians entering No. 10. The public watches footage closely to see whether VIPs can secure a quick scratch behind Larry’s ears, or—in former Prime Minister Liz Truss’s case—are left clutching air.

A recent survey showed Larry was more popular than either Starmer or Sunak, now the opposition leader.

There is a long tradition of cats at British government offices, since many Victorian-era buildings get their share of rodents. Neville Chamberlain’s mouser Bob (nicknamed the Munich Mouser, for his owner’s infamous botched peace deal with Hitler) apparently didn’t get along with Winston Churchill’s cat Nelson.

Churchill reputedly told his education minister Rab Butler that Nelson, who sat on his lap during meetings and thereby “acts as a hot water bottle and saves fuel and power," was doing more for the war effort than Butler.

Write to David Luhnow at david.luhnow@wsj.com