Profile: Jo Johnson, the younger brother who beat Boris into No 10

We've spent a lot of time talking about the possibility of a Johnson getting into Downing Street – and now it's finally happened. Few expected it would be Jo Johnson, the unassuming younger brother of Boris, who got into No 10 first.

The mayor of London will have spent his breakfast musing over the headlines about the appointment of Jo Johnson, the MP for Orpington, being elevated to the government. He is David Cameron's new head of policy in No 10 and a full Cabinet Office minister.

Squint your eyes and view them from afar, and you might just mistake Jo for his elder brother. They both have the same blonde mop, although Jo's is tidier and more measured. Both went to Eton College. Both belonged to the Bullingdon Club while at university at Oxford. Boris and Jo are undoubtedly cut from the same cloth – even if Jo's waistline is not quite as expansive.

In one critical way, though, Jo differs from his elder brother. He is not ostentatious. He does not get himself stuck in zipwires. Instead, after being elected to his Orpington seat in 2010, he has adopted a studied loyalty in his job as an assistant whip for the government. All whips are kept out of the headlines; it is their role to be, in the words of Francis Urquhart, the "backroom boy" who keeps the parliamentary party in shape by "giving them a bit of stick". Jo is certainly that. He has 3,640 Twitter followers, compared to his brother's 685,234.

This explains why Johnson's parliamentary career has been entirely unremarkable. His Twitter bio doesn't even acknowledge his job; he is merely described as "president of Orpington Football Club". According to theyworkforyou, he has spoken in just 14 debates in the last year, well below average among MPs although in line with whips. The same website notes he has used three-word alliterative phrases 27 times in debates – again, well below average among MPs. That compares to the 111 times used by Boris during his time in parliament. A clear indicator that the two brothers are, ultimately, very different politicians.

Even Jo Johnson's arrival in parliament was under the radar. He was only selected for the Orpington seat on December 2009, less than five months before polling day, but managed to notch up an eye-watering 59.7% of the vote, much more than twice the total of his nearest (Liberal Democrat) challengers. Before then Johnson had notched up some experience working for Deutsche Bank. He then joined the Financial Times in 1997. The newspaper posted him to Paris from 2001 to 2005 and then New Delhi from 2005 to 2008. After returning to London he headed the paper's Lex column, a job viewed as one of the most influential posts in financial journalism.

Cameron has slowly been learning to appreciate Johnson's qualities since then. Jo's time in New Delhi meant he was an obvious candidate to accompany the prime minister on his business trip to India in 2010. Now Johnson becomes Cameron's new head of policy. The job fills a gap in No 10 which had been developing for several months, after the requirements of coalition had left Downing Street dangerously underpowered. Now, with the general election two years away, Cameron is boosting up the political element of his No 10 team. Johnson joins an outfit that now also includes former energy minister John Hayes as a 'senior parliamentary adviser', as well as a cohort of other troublemaking backbench MPs – including Jesse Norman, George Eustice and Paul Uppal. Together they will attempt to break the will of right-wing Conservative malcontents gunning for the coalition's demise before 2015.

It will be a difficult task, requiring an active brain and one willing to work behind the scenes to get things done. Intelligence and discretion are valuable qualities – especially when they go together. They do not in Boris Johnson, but they certainly do in his younger brother. In a single stroke, he has slid into a position which undoubtedly makes him more powerful than the mayor of London. The new soap opera of British politics has arrived.