As Putin’s tanks rolled into Ukraine in February 2022, Catrin Vaughan’s parents made a frantic call to their daughter in Russia. “Please come home,” they pleaded with her.

Her father Alun was terrified she was alone in a nation full of “bandits”. He had often queried his daughter's decision in 2007 to leave their Carmarthenshire village to be a Russian billionaire’s nanny. Now, he was insistent she needed to leave as quickly as possible.

But despite war raging in Ukraine and the majority of her oligarch employers being hit with sanctions, Catrin, 43, had her own blunt reply to her parents’ urgent request to return.

“I just thought, ‘no, I'm going to stay here’,” she tells the Express. “I've got a lovely family. A billionaire boss and they're throwing money at me.”

Ever since their emergence following the breakup of the Soviet Union, nouveau riche Russian billionaires have been keen to hire a British nanny to ensure their children speak the Queen’s English and possess high-society manners.

The combination of that strong demand and their bottomless bank accounts has meant salaries for roles looking after oligarch offspring run to a staggering £180,000 per year – far outstripping the average £32,000 they can earn back home.

As each family covers the costs of food, accommodation, medical bills and travel for their employee, nannies such as Catrin, who adopts a well-spoken English accent with the families, banks a huge sum every month – not that she will admit how much it is.

War and sanctions have made it harder for Brits to be paid by oligarchs but the Express has discovered there are still many who, like Catrin, are ensuring the Russian elite have children brought up with British manners.

And as the brutal military campaign in Ukraine continues, we have gained unprecedented access to this unseen world of private jets and superyachts, lie detector tests – and children with no boundaries.

Firmin Shepherd, 43, fell into work as an English governor for Russia’s ultra-rich after taking on private tuition work during a spell studying at university in St Petersburg. Hailing from Canterbury and with an archetypal Home Counties accent, he found he could earn huge sums working for oligarchs.

He discovered two types of billionaires. One was so stuck up that they only saw “black caviar, champagne and private jets,” while the other valued everything “down to a single ice cream”.

Unlike Catrin, he was terrified when the war in Ukraine escalated.

“I have a couple of grey hairs today, which I swear appeared at the point when people started bandying about the ‘nuclear’ word,” he says

“[But] I was working for the kind of people who could easily be going to church with the president. You can't imagine they would allow themselves to be in a position where they could be at any risk from drone strikes or any other kind of military threat.”

Firmin says he regularly sees large air defences positioned strategically around Moscow and hears the “extremely loud” noises they make shooting down drones.

“One of them actually fell not far from my old apartment,” he says. “That didn't do anything to calm my nerves.”

His mother has visited numerous times and plans to come to see him in Moscow this year – entry to the country is via Turkey or Dubai these days.

But other family members view his life in Russia rather differently.

“I have a cousin who loves to put me on the spot and say to my face that I sound like a Russian apologist,” he adds.

When the billionaires decide they want their own Mary Poppins, they tend to turn to Moscovite Valentin Grogol, 40, who has run the English Nanny agency since 2009.

Now based in Dubai, he has some incredibly wealthy figures on his client list. One is Diora Usmanova, the niece-in-law of former Arsenal and Everton football club shareholder Alisher Usmanov. Her family has such prestige in the ex-Soviet state that she is often described as an Uzbek 'princess'.

Messaging app Telegram’s founder Pavel Durov's ex-wife, Irina Bolgar, is another for whom Valentin has sourced nannies. His first client was Anzhelika Khan, whose husband German was one of the first oligarchs to be hammered by UK sanctions.

His agency first came to the world's attention last year, when a report by investigative outlet the Dossier Centre claimed it was helping Vladimir Putin find a carer for the “secret sons” he allegedly sired with former Olympic gymnast Alina Kabaeva.

Valentin says he “can’t comment” on clients. But as his agency is “number one” among the elite, it’s unsurprising it would be cited in this type of “rumour”.

The Russian set up his agency after finding it ”very expensive and complicated” to find a native Brit to care for his own daughter. As he developed his company, he streamlined the process for making hires.

These checks, for instance, don’t just involve verifying diplomas and trawling social media feeds; most families insist their new hire gets a full medical MOT.

Some families go even further. One client made Catrin take a polygraph test to check she wasn’t a drug taker or might be tempted to steal wads of cash left around the house.

The profile of who makes the grade for the job, which often requires being on-call 24 hours a day or travelling to a remote part of the world at a moment's notice, is varied.

“Even if the person has a great education, sometimes they cannot work with children,” he says. “Lessons [are] not the only work they have to do. During [a typical] day they might be doing sports, giving food, checking the children’s clothes or putting sun cream on.”

Nearly all of the nannies I spoke to had worked in unglamorous environments, such as cleaning or working with children in care, before serving the ultra-rich.

But since the full-scale invasion of Ukraine in 2022 and the subsequent sanctions placed on Russia, Valentin has added one essential requirement: no politics. At all.

“We ask them, ‘What is your opinion [on Russians]? – are you OK to fly to Russia? Do you feel any hatred against Russia?” he says.

“We check as much information as we can. We are trying to find politically neutral people.”

Valentin’s oligarch clients also demand that staff prioritise privacy.

An employee who wants to post pictures of their holiday alongside their clients in the Maldives will find themselves unemployed fast. And everyone I spoke to for this story did so on the basis that they wouldn’t name any of their clients.

Surprisingly, friction with the Russian state is apparently limited, as the families they work for occupy a world of private jets and golden visas meaning the law hardly applies.

Yet one English nanny, who spoke to me on the condition of anonymity, did reveal she’d been grilled by Russian officials when the war in Ukraine first began.

“I was asked about my political views on the UK and Russia,” she says. “They check your phone and things like that, but that only happened once.

“I think the fact that you're living in the country means they automatically accept you as somebody that has respect for their culture.”

In this nanny’s experience, the biggest challenge came from handling the children.

“They are spoiled to the hilt,” she says. “It can be so extreme that they can choose to see a band, travel abroad for the concert and then come back two days later.”

And, of course, being thoroughly spoiled is not necessarily beneficial to the children’s development.

“A lot of rich kids are very, very dysfunctional psychologically, educationally, certainly behaviorally,” she admits. “I worked with foster kids and then with very rich kids [and] the behavioural differences are not that far apart at all.”

Having spent the best part of two decades working around the world caring for the children of wealthy families, she is thinking about what her next career move will look like.

But, there is a problem. All the money she’s accumulated cannot be spent in Britain, after the severing of economic ties following the invasion of Ukraine.

“I’ve been trying to buy a house,” she adds. “[But because] I still have a connection to Russia, every solicitor I tried wouldn't touch me. They are too scared.”

But regardless of international tensions, the appeal of British nannies is unlikely to diminish among Russia’s elite.

Yulia Serykh, 36, who has huge interests in Russian agriculture and property, has been employing Brits through Valentin’s agency to look after her son since he was a toddler.

Like everyone we spoke to, she placed the accent at the top of her list of reasons why an English nanny was preferable to any other.

“I think pronunciation is very important,” she says. “I didn't want a Filipino nanny who speaks English, but with an accent.”

All the nannies I spoke to were enthusiastic about the stays in luxury hotels, Michelin-star dinners and worldwide travel their job has let them experience.

Catrin, in particular, was proud that a girl from Wales now has enough money to buy properties around the world, while spending her summers on superyachts.

But the war in Ukraine has resulted in many of her old friends blocking her on social media, limiting the people with whom to spend her money.

And regardless of how luxurious the environment might be, she can’t deny feeling isolated from the rest of the world. “I'm perpetually lonely,” she adds, “and I've got used to it because I've been ostracised.”

Which goes to show that even the most privileged jobs may end up not being worth it in the long-term.