- Video report by ITV News Political Correspondent Libby Wiener
Before Mr Johnson was formally anointed as Britain's new leader, it was announced that former Vote Leave director Dominic Cummings - seen in Downing Street wearing a T-shirt while others were suited and booted - would be joining as a senior advisor.
Mr Cummings will act as Mr Johnson's de facto chief of staff, helping the former Mayor of London to execute his Brexit vision for Britain.
As the mastermind behind the Vote Leave campaign, Mr Cummings - who was played by Benedict Cumberbatch in James Graham's TV recreation of the campaign earlier this year - divides opinion among MPs.
The Oxford-educated 47-year-old has been widely credited with the famous £350m pledge for the NHS which was made during the 2016 referendum.
Now Mr Johnson has appointed Mr Cummings, along with other former Vote Leave staffers, including Lee Cain as director of communications, Robert Oxley as press secretary and Oliver Lewis as Brexit policy adviser, there will be pressure on Mr Johnson to deliver on the promise which was plastered across that red bus.
It is not only the promise painted across the red bus for which Mr Cummings is both revered and despised for in the House of Commons.
In his lengthy blogs posts, Mr Cummings has frequently spoken out against Parliament's inability to deliver on Brexit, criticising the decision to trigger Article 50 so quickly.
What will also appear to some Conservative MPs is his criticism of the civil service. He has previously said the institutions tasked with delivering government policy are "programmed to fight to stay dyfunctional" and "fight to exclude the most able people".
An overhaul of Whitehall may send shivers down the spines of special advisers, but what will anger some MPs is how a man who was in contempt of parliament has now secured himself a job at Number 10.
Mr Cummings was reportedly asked to appear before a hearing into fake news over allegations made against Vote Leave, to which he did not show.
Following his hiring, former Conservative-turned-independent MP Sarah Wollaston told ITV News: "I think it's an extraordinary error of judgement to appoint someone who has been found in contempt of parliament for refusing to give evidence to select committees after being formally instructed by the House to appear."
The newly-appointed Transport Secretary Grant Shapps defended Mr Johnson's decision to hire Mr Cummings and other Vote Leave staffers.
"What Boris likes to do, and I've noticed this working with him, is bring in lots of different views, lots of different advice, and he will make his decisions in his own time, and he's very good at doing that," Mr Shapps said.
"What he wants is the best brains around him, and Cummings has obviously got, whatever people think about him, a particularly big brain."