Twenty-five years ago Kwasi Kwarteng appeared on page three of The Sun newspaper after muttering “oh fuck, I’ve forgotten” during an episode of the TV quiz University Challenge.

Now the 45-year-old MP for Spelthorne in Surrey is making rather different headlines, as the first black Conservative MP to lead a British government department.

The new business secretary, the son of Ghanaian parents, won a scholarship to Eton and studied classics and history at the University of Cambridge.

He became a financial analyst at banks including JPMorgan before turning his hand to politics and writing books on subjects ranging from Margaret Thatcher to a history of the finances of European empires.

A rightwing intellectual, he has studied Arabic in recent years and read Thomas Piketty’s Capital in the 21st Century in its original French.

Mr Kwarteng, a former chair of the Bow Group, a traditional Tory think-tank, is one of a clique of free marketeers who entered parliament in 2010 and now sit in the cabinet.

Along with international trade secretary Liz Truss, foreign secretary Dominic Raab and home secretary Priti Patel, he wrote a booklet called Britannia Unchained in 2012, which caused a stir with its criticism of Britain’s supposedly lazy workforce.

They described the British as “among the worst idlers in the world”, criticised unionisation, and said “fear of unemployment and unfair dismissal has led to a system of employment law that discourages small businesses from taking a risk”.

Britannia Unchained also dismissed the idea of actively trying to narrow the north-south divide, which is now official Tory government policy.

Yet Mr Kwarteng, who was previously energy minister, has resisted pigeonholing as a knee jerk rightwinger. He recently accepted the need for government intervention in energy markets, accelerated the reform of the Big Four auditors and triggered an attempt to bar former directors of collapsed contractor Carillion from future directorships.

“There’s nothing [better] to convert someone from being a radical free marketeer to seeing the virtues of government action than making them an energy minister,” he told a 2019 Tory party conference event.

While his co-authors of Britannia Unchained achieved rapid ministerial promotion, the arch Eurosceptic Mr Kwarteng did not enter government until 2018, when he became a junior minister in the Department for Exiting the European Union.

There he prompted controversy for suggesting that the public thought judges, caught in a Brexit storm, were “biased”.

His rapid recent ascent should be seen in the context of him twice backing Boris Johnson for the Tory party leadership, in 2016 and again in 2019, when he was one of the first MPs out of the blocks in support of the eventual winner.

Mr Johnson rewarded him with the energy portfolio in the business department (BEIS), a stepping stone to his new role.

Tristram Hunt, head of the V&A Museum and a former Labour MP, was roommates with Mr Kwarteng when the latter was writing his PhD at Cambridge university on the recoinage crisis of 1696.

Mr Hunt said Mr Kwarteng’s progress was initially stymied because previous prime minister David Cameron and his chancellor George Osborne did not like him.

“The joy of Kwasi is that he is quite ungovernable and has views that he likes to express, like Boris he is disheveled and doesn’t fit what George and David regarded as the self-discipline of a professional politician,” he said.

“There is a breadth and richness to him and a kind of iconoclasm to him, although it’s clear that he did buckle down and impress people in his last role as energy minister.”

Some executives in the energy sector said they had never had as much access to a minister and that Mr Kwarteng had been hands-on with regular calls during the pandemic.

His main achievement was overseeing the government’s first sectoral white paper for 13 years, with ambitious plans to decarbonise the UK’s energy system.

One industry figure said that unlike some of his predecessors, Mr Kwarteng did “make decisions quickly” and challenged people to find out what the problems were and how to get things done.

While he can be courteous and thoughtful, some executives described him as “short and brisk”.

“He doesn’t suffer fools,” said one colleague. “He’s basically hung up on some serious players if they don’t provide what he’s after.”

There are clues as to how Mr Kwarteng might want to run BEIS both in Britannia Unchained and in a pamphlet he wrote in 2013 called The Innovation Economy.

Britannia Unchained argued that subsidies for renewable energy were wrong and that a “viable industry should not require that level of public subsidy”.

In The Innovation Economy he argued that industrial policy had had a “very mixed record” and, in some cases, held back Britain’s postwar economy. He also wrote that the smallest new companies should be exempted from all employment legislation and business taxes for their first three years.

Green campaigners may also be unnerved by House of Commons records showing that Mr Kwarteng received £20,500 before the last election for his campaign from companies and individuals with links to the oil industry.

Yet Mr Kwarteng has moderated his free market instincts and accepted the need for government to accelerate a shift towards the low-carbon economy, according to observers.

He was heavily influential in convincing the Treasury to launch its first green bond, which was announced late last year. He also pushed hard for a new lending bank focused on low-carbon projects, an idea that led to the creation of the National Infrastructure Bank.

Mr Hunt said his old friend, who got married in 2019, would have made an excellent historian: “He’s someone who is very much at home in an institution, whether university or parliament. He’s usually happy so long as he has a warm canteen lunch on a tray at 12.30pm.”