EXCLUSIVEWatch out Larry, there's a new top cat in town: Keir Starmer brings in family moggy JoJo to Number 10 - leaving Downing Street's Chief Mouser VERY unimpressed 

Number 10 could be plunged into cat-astrophe over fears of a feud between Chief Mouser Larry and Keir Starmer's moggy JoJo when the new Prime Minister moves his family in to the Downing Street residence.

Notoriously territorial Larry, 17, has served the Cabinet Office since 2011, living in Britain's must famous address under six prime ministers.

The no-nonsense moggy has gained a reputation for warning off rivals, famously taking on and chasing away a huge fox in 2022.

His relationships with other cats has also been testy - maintaining a four-year feud with his former nemesis the Foreign Office's Chief Mouser Palmerston, who retired from his post in 2020.

And now Starmer's first piece of high-profile diplomacy could be to convince Larry to put aside his differences as he welcomes his counterpart into his new home, as the PM says JoJo is 'revered' by his children.

But a moggy behavior manager says tensions could flare if the Chief Mouser feels 'threatened' by his new counterpart.

Nicky Trevorrow, of Cats Protection, told MailOnline: 'It's natural for cats to feel threatened when a new cat comes along, as they'll be protective of their territory and all the perks that come with it – like food, shelter and warmth. 

Notoriously territorial Larry, 17, has served the Cabinet Office since 2011, now living in Britain's must famous address under six prime ministers

Notoriously territorial Larry, 17, has served the Cabinet Office since 2011, now living in Britain's must famous address under six prime ministers

And now Starmer's first piece of high-profile diplomacy could be to convince Larry to put aside his differences as he welcomes his counterpart to his new home. Pictured: Sir Keir and his wife Victoria pose outside 10 Downing Street after being appointed PM

And now Starmer's first piece of high-profile diplomacy could be to convince Larry to put aside his differences as he welcomes his counterpart to his new home. Pictured: Sir Keir and his wife Victoria pose outside 10 Downing Street after being appointed PM

His relationships with other cats has also been testy - maintaining a four-year feud with his former nemesis, the Foreign Office's Chief Mouser Palmerston, who retired from his post in 2020. Pictured: Larry and Palmerston scrap in 2019

His relationships with other cats has also been testy - maintaining a four-year feud with his former nemesis, the Foreign Office's Chief Mouser Palmerston, who retired from his post in 2020. Pictured: Larry and Palmerston scrap in 2019

A moggy behavior manager says tensions could flare if the Chief Mouser feels 'threatened' by his new counterpart

A moggy behavior manager says tensions could flare if the Chief Mouser feels 'threatened' by his new counterpart

'That's why it's important to take it really slowly, keep them in separate areas and get them used to each other's scent before they actually see each other. When they're familiar with another cat's smell, it'll make the face-to-face introduction much easier.

'The worst thing to do is to put the cats together on day one and hope they'll sort it out themselves. 

'It's too much of a shock and both cats will be on their guard which will most likely lead to aggressive behaviour. In turn this can cause them to be stressed and it may make the whole process slower in the long run.'

British domestic tabby Larry was born as a stray in 2007 and was adopted by Downing Street staff from Battersea Dogs and Cats Home in 2011.

He is the first cat to be bestowed with the official title Chief Mouser, with the government describing his role as 'inspecting security defences and testing antique furniture for napping quality' alongside 'contemplating a solution to the mouse occupancy of the house'.

Unfortunately for parliament's occupants, this is still 'in tactical planning stage'. 

His previous battles with Palmerston repeatedly garnered media attention - with the pair being caught in a serious cat fight in 2016. Larry walked away without his collar and the Foreign Office moggy received a damaged ear. 

Larry's previous battles with Palmerston repeatedly garnered media attention. Pictured: Palmerston in 2019

Larry's previous battles with Palmerston repeatedly garnered media attention. Pictured: Palmerston in 2019

British domestic tabby Larry was born as a stray in 2007 and was adopted by Downing Street staff from Battersea Dogs and Cats Home in 2011

British domestic tabby Larry was born as a stray in 2007 and was adopted by Downing Street staff from Battersea Dogs and Cats Home in 2011

They were later frequently spotted yowling at each other as gathered press spectated their stand-offs from outside Downing Street.

In 2012, police also had to break up a fight between Larry and ex-Chancellor George Osborne's cat Freya. 

Starmer has repeatedly spoken of his fondness for his own cat JoJo, who is also a rescue.

He told BBC Derby: 'We've got a cat called JoJo, revered by the kids.

'JoJo was a cat we got from a rescue centre. JoJo is treated with far more respect in our household than I am.

'When I walk through the door I have to put the baggage of being Leader of the Labour Party down, I'm Dad and I'm fair game for the kids to ridicule me, laugh at me etc.

'But JoJo, on the other hand, if JoJo wants food, or a seat on the settee, or to sit on the kid's bed he's got pride of place.'

The family may also fear for his daughters' hamster Bear given Larry's reputation as a 'good ratter' - after he revealed the little animal already lives in fear of JoJo.

Laughing to Metro in 2022, he said: 'We have got a cat and trying to keep the hamster and the cat apart has been one of the major issues of the last few weeks.

'No doubt our daughter will make a big case for the hamster to travel with us.'

Mr Trevorrow says that all is not lost - and even suggested that through a careful approach JoJo and Larry could form a 'strong bond'.

He is the first cat to be bestowed with the official title Chief Mouser, with the government describing his role as 'inspecting security defences and testing antique furniture for napping quality' alongside 'contemplating a solution to the mouse occupancy of the house'

He is the first cat to be bestowed with the official title Chief Mouser, with the government describing his role as 'inspecting security defences and testing antique furniture for napping quality' alongside 'contemplating a solution to the mouse occupancy of the house'

The no-nonsense moggy has gained a reputation for warning off rivals, famously taking on and chasing away a huge fox in 2022

The no-nonsense moggy has gained a reputation for warning off rivals, famously taking on and chasing away a huge fox in 2022 

He continued: 'As is often the case, rewards can be a great help when it comes to building good relationships. When the two cats do meet each other, and if they're both calm and relaxed, a little treat will go a long way to helping them feel good about the relationship. This doesn't need to be food - a little fuss or attention is just as good.

'Both cats should be given plenty of space and time while they become familiar with each other. 

'Strong bonds take time to build, but if plenty of time and care is taken there is no reason why Larry and JoJo can't go on to build a successful alliance in Westminster.'

Number 10 has been contacted for comment. 

Downing Street has seen a succession of pets as the nation's prime ministers enter the residence alongside their families.

In September 2023, Larry was said to have come out 'on top' in several heated clashes with Rishi Sunak's fox red labrador retriever.

Akshata Murty, the Prime Minister's wife, said the family dog Nova had 'mixed emotions' about Larry and that the pair didn't always get on. 

'Nova has mixed emotions because she sometimes doesn't get on with Larry the cat,' she told Sky News. 

Boris Johnson's dog Dilyn also stirred up controversy - as the former PM struggled to control the Jack Russell cross' 'romantic urges'. Pictured: Carrie Symonds with Dilyn

Boris Johnson's dog Dilyn also stirred up controversy - as the former PM struggled to control the Jack Russell cross' 'romantic urges'. Pictured: Carrie Symonds with Dilyn

Akshata Murthy walks Nova
Akshata Murthy walks Nova

Akshata Murthy is pictured at the back of Downing St returning from walking red labrador Nova, September 4

'And they've had some heated exchanges and Larry's come out on top.

'So she might have some mixed opinions on living here. But, you know, our family is so grateful to be here.'

Boris Johnson's dog Dilyn also stirred up controversy - as the former PM struggled to control the Jack Russell cross' 'romantic urges'.

Speaking to dog handlers in 2021 he complained that his and Carrie's pet was 'endlessly' up 'on people's legs' in Downing Street. 

In a bid to slow his rampant libido, it was later reported that the Johnsons were force to neuter the pup - who was said to have had his own feud with Dominic Cummings after an attempted romantic tryst with the advisor's leg at Chequers.

Larry was initially brought in to deal with a rat problem in Downing Street, with a spokesperson saying he was a 'good ratter'.

He was known to have a 'very strong predatory drive' developed in his time on the streets and is said to enjoy playing with toy mice.

In a statement on his arrival, Mr Cameron said: 'I'm delighted to welcome Larry to his new home.

'He came highly recommended to me by Battersea Dogs and Cats Home, who did a fantastic job looking after him.

Larry's predecessor, Humphrey, was adopted in 1989 and wandered Number 10 as a stray while Margaret Thatcher and John Major were prime ministers

Larry's predecessor, Humphrey, was adopted in 1989 and wandered Number 10 as a stray while Margaret Thatcher and John Major were prime ministers

He moved out six months after Tony Blair took power in 1997 - with his wife Cherie being forced to deny reports her dislike for the moggy was the reason. Pictured: Cherie and Humphrey

He moved out six months after Tony Blair took power in 1997 - with his wife Cherie being forced to deny reports her dislike for the moggy was the reason. Pictured: Cherie and Humphrey

Humphrey was cared for in his 'retirement' at the home of a civil servant, before passing away in March 2006

Humphrey was cared for in his 'retirement' at the home of a civil servant, before passing away in March 2006

'I'm sure he will be a great addition to Downing Street and will charm our many visitors.'

The residence also has a long history of cats - Larry's predecessor, Humphrey, was adopted in 1989 and wandered Number 10 as a stray while Margaret Thatcher and John Major were prime ministers.

But he moved out six months after Tony Blair took power in 1997 - with his wife Cherie being forced to deny reports her dislike for the moggy was the reason.

He was cared for in his 'retirement' at the home of a civil servant, before passing away in March 2006.

Before Humphrey, the home played residence to a kitten called Wilberforce, who was aquired from the RSPCA by Edward Heath.

Thatcher was said to have brought him back a tin of sardines from a trip to Moscow before he retired in 1986.

Labour PM Ramsay MacDonald also had a renowned rat-catcher called Rufus of England, which lived in Number 10 in the 1920s - although he was given the less grand nickname 'Treasury Bill'.

Winston Churchill's cat Nelson - formerly a stray - also clashed with Neville Chamberlain's 'Munich Mouser' when the former took over as Prime Minister during the Second World War in 1940. 

According to the Telegraph, their dispute became famous on both sides of the Atlantic after newspapers in the US speculated on how the two could co-exist once Churchill took power.

It is believed Nelson won the battle as the black cat was often seen with his master at war cabinet meetings.

He famously won favour with Churchill after chasing away a dog in front of the war leader, who was taken with Nelson's 'bravery'.