David Cameron's return puts a grown-up at the heart of Rishi Sunak's team

Cameron was a six-year British prime minister who returned the Conservatives to office

Britain's new Foreign Secretary David Cameron, fourth right, attends his first Cabinet meeting at No 10 Downing Street. AP

Mr Cameron speaks with Prime Minister Rishi Sunak as he is appointed Foreign Secretary. Photo: No 10 Downing Street

Mr Cameron arrives at 10 Downing Street, seven years after he stepped down as prime minister. Reuters

Mr Cameron alongside fellow former Prime Ministers Gordon Brown, Tony Blair and John Major at the Remembrance Sunday ceremony at the Cenotaph in London. Getty Images

David Cameron at the National Service of Thanksgiving to Celebrate the Platinum Jubilee of Queen Elizabeth II at St Paul's Cathedral in London in 2022. Getty Images

Mr Cameron leaves his home in London to give evidence to a select committee on Greensill in 2021. Getty Images

David Cameron resigned as Prime Minister outside 10 Downing Street in June 2016. Getty Images

David Cameron on his campaign bus in 2016 on the final day of campaigning on whether Britain should remain or leave the EU. Getty Images

China's President Xi Jinping and David Cameron at a joint press conference in 10 Downing Street in 2015. Getty Images

David Cameron stands with then-London Mayor Boris Johnson in 2012. Getty Images

Vladimir Putin with David Cameron at the London 2012 Olympic Games. Getty Images

Mr Cameron is greeted by wellwishers during a visit to Tripoli in September 2011. Getty Images

Mr Cameron and US President Barack Obama walk in the gardens of Lancaster House in 2011. Getty Images

David Cameron and George Osborne at a signing ceremony at the Great Hall of the People in Beijing, in 2010. Getty Images

David Cameron with Deputy Prime Minister Nick Clegg on their first day of coalition government on May 2010 in London. Getty Images

Queen Elizabeth greets David Cameron at Buckingham Palace for an audience to invite him to be the next Prime Minister, in May 2010. Getty Images

Former Conservative Party leader David Cameron, Liberal Democrat leader Mr Clegg and then-Prime Minister Gordon Brown debate during the third and final leader's debate in Birmingham in 2010. Getty Images

David Cameron at the Great Brook Charity run in 2009 in Chadlington, Oxfordshire. Getty Images

David Cameron, George Osborne and William Hague walk to the International Conference Centre during the Conservative Party conference in 2008 in Birmingham. Getty Images

David Cameron waves to supporters with his wife Samantha after winning the leadership election in 2005 in London. Getty Images

David Cameron celebrates with supporters at his constituency office in 2005 in Witney, Oxfordshire. Getty Images

David Cameron used his LinkedIn account last week to make a rare post-ministerial intervention in UK politics, perhaps signalling that Rishi Sunak's government could take on the unfinished business of his 2010-16 administration.

Applauding a measure in the King's Speech to establish a Holocaust Memorial near the Houses of Parliament, Mr Cameron referred to the row engulfing Westminster on how to respond to the fallout from the Israel-Gaza conflict.

"At a time when the scourge of anti-Semitism, prejudice and intolerance are very sadly on the rise, the need for this national memorial has never been more vital," Mr Cameron wrote.

"Today’s announcement takes us a step closer to making this a reality and fulfilling the promise I made almost a decade ago."

Mr Cameron was a one-and-a-bit term British prime minister who returned the Conservatives to office after "detoxifying" the political brand, but for the first five years only in a coalition with the Liberal Democrats. Having won a majority in 2015, he suffered the humiliation of losing a referendum on Brexit that he had called to cement the Conservatives grip on power.

Four Conservative prime ministers then followed, with Rishi Sunak the latest to take the reins late last year.

Out of office, Mr Cameron was a passionate campaigner for Alzheimer’s Research and spearheaded an initiative on failing states at the Council on State Fragility at International Growth Centre.

In January he accepted a teaching position at New York University Abu Dhabi to lecture students on politics in the age of disruption during a three-week course.

A moderate in the party, Mr Cameron was born into privilege and went to the elite Eton school. He was a promising student of politics and economics at Oxford and then worked as a press officer for then-Conservative leader Michael Howard before becoming an MP in 2001.

In a statement on Monday, he referred to his seven year absence from the political front line and even some recent public criticism of Prime Minister Rishi Sunak, notably the decision to scrap the High Speed rail project in northern England. "Though I may have disagreed with some individual decisions, it is clear to me that Rishi Sunak is a strong and capable Prime Minister, who is showing exemplary leadership at a difficult time," he said. "I want to help him to deliver the security and prosperity our country needs and be part of the strongest possible team that serves the United Kingdom and that can be presented to the country when the General Election is held."

As prime minister, Cameron ordered military intervention in Libya, when Britain and its allies led international efforts to help oust then-leader Muammar Gaddafi in early 2011.

Cameron is not a serving MP so has been made a Lord for his ministerial role. The appointment of Lord Cameron was unseen move for almost all in Westminster, not just because of the return of a former prime minister to government – the first since Alec Douglas-Home – but also because of his views on China.

During the Cameron administration there was a “golden era” of UK-China co-operation, something Mr Sunak described as “naive” last year following growing tensions with Beijing.

The last foreign secretary to serve from the Lords was Lord Carrington, who resigned on a matter of principle during the Falklands War before going on to become Nato Secretary General. If Development Minister Andrew Mitchell stays on it is expected he will answer questions in the Commons for the foreign secretary.

The move also revives memories of the personalities involved in the course of Brexit as the referendum campaign got underway. Some of his most loyal lieutenants including justice minister Michael Gove -- godfather to one of Cameron's children -- said they would campaign for Brexit.

Then Boris Johnson, who went on to become prime minister but who at the time was London mayor, sprung a surprise by also backing "Leave". Mr Johnson was an Eton contemporary of Mr Cameron and the pair were not natural allies.

During the campaign, Mr Cameron led from the front with a barrage of speeches arguing that Britain's economy would be badly hit by Brexit. The "Leave" camp's counter argument that immigration from EU countries needed to be cut to reduce the strain on public services, was the one that resonated most with voters.