He’s on his sixth prime minister, has watched presidents and princes walk through the black door of No 10, and will soon become the longest continuous resident of Downing Street since Pitt the Younger.

The landscape of British politics has changed a lot in the past 15 years, but Larry the cat has remained a reassuring constant. Now his enduring popularity – the like of which some of his temporary owners would kill for – is to feature in a new Channel 4 documentary series exploring Britain’s love of cats. For his fans, the spotlight has been a long time coming.

“Larry’s totally the guy to meet in No 10,” one Westminster source said, adding that – as police officers stationed outside the entry of No 10 who regularly open the door for him will attest – he “has the run of the house”.

Larry, whose official title is chief mouser of the Cabinet Office at 10 Downing Street, slunk into the heart of the UK government after being adopted from Battersea Dogs & Cats Home to address a rodent problem.

His is a rats to riches story to put any schmaltzy political biography to shame. Found as a stray in Wandsworth, he arrived in Westminster in 2011 with David Cameron and Nick Clegg’s coalition government in its infancy.

If tensions were high between the unlikely governmental bedfellows, Cameron was keen to dispel any animosity between him and the nation’s new favourite feline. “The rumour is I don’t love Larry – I do,” he declared at one PMQs.

A more established figure now than he was back then, Larry seems to have adjusted to the glare of the spotlight. Often spotted on live broadcasts waiting patiently by the front door, his relaxed demeanour in front of a watching audience has become a nuisance to the the Downing Street gardener – Larry often visits the front flower patch to do his business.

His official government page describes the 18-year-old tabby as spending “his days greeting guests to the house, inspecting security defences and testing antique furniture for napping quality” and lists his day-to-day responsibilities as “contemplating a solution to the mouse occupancy of the house”.

Although he is the first cat to hold his specific title, cats had been welcomed into the corridors of power for at least a century, explained Philip Howell, a professor of geography at the University of Cambridge, who has written extensively about the human-animal relationship. “Stability is an essential part of Larry’s appeal,” he said.

“Larry gives the public some much-needed continuity and nonpartisan continuity at that.”

Justin Ng, a photographer often present in the press pen outside No 10 who has become firm friends with Larry over the years agrees. He said: “His steadfastness and his unparalleled ability to appear at the right moment and pose for all of us makes him so endearing to everyone.”

“The minute something happens on the street, especially an official visit, like clockwork, he’ll be out the front,” a Downing Street source said. “He loves the red carpet.”

The former US president Barack Obama and the Ukrainian president, Volodymyr Zelenskyy, are just some of the world leaders he has charmed. But not all leaders were so enamoured.

“Theresa May famously hated him because she was a dog person,” said Ng, who has witnessed a few MPs trying, and failing, to stroke Larry (Matt Hancock and David Lammy are on the list).

The former Scotland secretary Ian Murray went as far as to describe Larry as a “little shit” because he refused to pose with the newly minted Labour cabinet, Ng said, adding: “Think Larry has had the last laugh on him.”

Like all political animals, Larry has experienced public scraps, most, notably with Palmerston, the cat who lived at the Foreign Office until he retired in August 2020. The two could often be seen fighting viciously, said a police officer on duty at No 10. Did police ever intervene? “Oh no, no. You don’t get involved in a cat fight,” the officer said.

Larry’s popularity with the public, meanwhile, is undeniable. There are various social media accounts dedicated to the nation’s top mouser, especially the witty Number10Cat X account that has more than 868,000 followers. Larry also receives fan mail, toys and treats from across the world and has recently featured in the journalist and former special adviser Peter Cardwell’s book, Political Animals.

When he’s not treading the pavements, Larry’s frequent sleeping spots include the printer and in-trays, but his favourite places are on the window sills on either side of the front door.

Ng says Larry’s brush and Dreamies are stashed in the Duke of Wellington’s chest of drawers inside the foyer of Downing Street – that much is known to the custodians, civil servants and officers he interacts with daily. Those who feed him or carry treats are Larry’s favourites.

As top cat, of course, Larry comes in for his fair share of criticism. The New Statesman’s political editor, Andrew Marr, recently went as far as to call Larry “too fat and too idle to actually do his job”, accusing him of being “welfare dependent”.

In these times of pre-budget belt tightening, sources close to Larry have issued a stinging rebuke. In fact, they say, Larry is not publicly funded, Downing Street staff voluntarily paying his costs. Fur enough!