Larry, the cat who has been serving as Chief Mouser to the Cabinet Office in Downing Street, became a problem for the to be prime minister's four felines.

Penny Mordaunt, the bookmaker's favorite to replace Boris Johnson in the famous residence, revealed in an online forum that she has a quartet of Burmese cats, which she cited when asked for her biggest weakness.

"Introducing them into Number 10 might present some challenges with Larry," she told the question-and-answer session hosted by the Conservative Home website.

A stalwart of the U.K. political scene, Larry has ruled the roost in Downing Street for more than a decade. In Larry's Twitter account, "15 year old tabby. Seen off three Prime Ministers. Awaiting my fourth lodger," description takes place.

Three Conservative Prime Ministers – David Cameron, Theresa May and Boris Johnson – have served under him. He arrived in 2011 aged four, after being adopted from a London animal shelter and chosen for his mousing skills.

Given the title Chief Mouser, he also has his own unofficial Twitter account – @Number10cat – with more than 635,000 followers.

Earlier this month, as the scandal-tarred Johnson announced he would resign once a successor is selected, Larry took to social media to "clarify a few things."

"1. I'm not 'Boris Johnson's cat' 2. Like all prime ministers, he's only a temporary resident of Downing Street 3. I live here permanently. When he finally goes, I stay 4. Yes, it's all very embarrassing but it will be over soon," @Number10cat tweeted.