Britain's new PM is almost a billionaire — with a net worth twice that of King Charles

LONDON — Britain's new Prime Minister Rishi Sunak made history as the country's first leader of color and its youngest in recent centuries, taking office aged just 42.

He also breaks the record for being the wealthiest-ever occupant of Downing Street — with a fortune estimated to exceed that of King Charles III.

Sunak, who on Monday succeeded Liz Truss as leader of the U.K.'s ruling Conservative Party, previously worked as a Goldman Sachs analyst and then a hedge fund manager, before becoming a politician eight years ago.

But he owes much of his vast fortune to his wife, Akshata Murty, a tech heiress whose father, N. R. Narayana Murthy — who spells his surname differently — founded the Indian IT company Infosys.

Together, the couple has an estimated fortune of £730 million ($844 million), according to the Sunday Times Rich List.

The majority of Murty's wealth derives from her 0.93% stake in Infosys — which currently has a market cap of around $75 billion. However, Murty also owns Catamaran Ventures U.K., the British arm of her father's venture capital and private equity firm, which has stakes in a portfolio of companies including a luxury furniture brand co-owned by Rupert Murdoch's eldest daughter.

Catamaran Ventures did not respond to CNBC's request for comment.

The couple, who met while studying MBAs at Stanford University, also reportedly owns at least four properties worth an estimated £18.3 million, including an apartment in California.

Before entering Downing Street, their main residence was a five-bedroom house in Kensington, London, worth an estimated £6.6 million, while they spent weekends at a Grade II-listed retreat in Yorkshire, according to The Guardian.

Sunak and his wife's personal fortune is well above that of the U.K.'s former richest prime minister, Edward Stanley, who was elected in 1852 and had a net worth of around $440 million in today's money, according to Guinness World Records.

It is also more than twice as much as the wealth of King Charles III and his queen consort, which is estimated at roughly £370 million.

That estimate excludes the value of the wider crown estate — a diverse portfolio of buildings, artworks, forests and fields worth billions of pounds — which is not owned personally by the king but rather held by the monarch only for the duration of their reign.

Sunak's installment as prime minister is thought to mark the first time the residents of Downing Street have been wealthier than the residents of Buckingham Palace.

It comes at a time when millions in the U.K. are facing a cost-of-living crisis, raising questions over multimillionaire Sunak's ability to understand the experience of ordinary Britons.

Indeed, the former finance minister came up against sharp criticism earlier this year over his wife's "non-domiciled" status, which excluded her from paying tax on her earnings outside the U.K. The loophole, though legal, is estimated to save the family £20 million in U.K. taxes.

Murty later promised to give up that status and start paying taxes on her full income. At the time of writing, Downing Street did not respond to CNBC's request for confirmation that she had done so.

Correction: Rishi Sunak worked as an analyst at Goldman Sachs. An earlier version misstated his position.