Gavin Williamson has been named as the new Defence Secretary following Sir Michael Fallon's resignation amid the Westminster sleaze scandal.
Sir Michael sensationally resigned on Wednesday after admitting his actions had "fallen below the high standards required" of the job.
The MP for Sevenoaks had previously apologised for touching a female journalist's knee during a dinner 15 years ago, amid allegations of inappropriate behaviour by Conservative MPs.
Mr Williamson was the Government's chief whip before being appointed to his new role and has no previous ministerial experience.
His replacement as Theresa May's parliamentary enforcer is Julian Smith, who was previously Mr Williamson's deputy.
The changes to the Prime Minister's top team also see Tatton MP Esther McVey return to Government as Mr Smith's deputy, having served as work and pensions minister from 2012-15.
But the limited reshuffle appears to have caused disquiet within Mrs May's party, with some perplexed at the swift rise of Mr Williamson.
In a text to Sky's political correspondent Lewis Goodall, one Tory MP said: "He's out of the ****storm. Knifed Fallon and pinched his job. It's way above his ability."
Most positive response I've had so far from a Tory MP on Gavin Williamson: "He'll be fine."
— Lewis Goodall (@lewis_goodall) November 2, 2017
In an apparent reference to the appointment, Tory MP Sarah Wollaston tweeted:
There are times when offered a job that it would be better to advise that another would be more experienced & suited to the role
— Sarah Wollaston (@sarahwollaston) November 2, 2017
Mrs May's official spokesman said Mr Williamson was not involved in reshuffle discussions, as chief whips often are.
He said Mrs May thinks Mr Williamson was an "excellent and hard-working chief whip and the Prime Minister thinks he will make an excellent Defence Secretary".
:: Who is Gavin Williamson?
He is known as "Chief" in Downing Street, keeps a tarantula called Cronus on his desk and is regarded as a vital part of the PM's inner circle.
Mr Williamson's elevation to Defence Secretary is the latest chapter in a remarkable rise, having been elected to represent South Staffordshire in 2010.
The 41-year-old was born and raised in Scarborough by Labour-supporting parents and went to a local comprehensive and sixth form.
After working at a pottery and an architectural design company he moved into politics, getting his big break as former prime minister David Cameron's parliamentary private secretary from 2013-16.
Mr Williamson then headed Theresa May's successful campaign for the Tory leadership in the wake of the EU referendum and became chief whip in the wake of the her election gamble misfire in June.
He was in the spotlight this summer as Mrs May manoeuvred to agree a deal with the DUP to support her minority government – and was captured on camera signing the final agreement.
The presence of Cronus on his desk is said to have given an added layer of menace to his efforts to keep errant MPs in check.
"You have to look at all different ways to persuade people to vote with the Government and it's great to have Cronus as part of the team," Mr Williamson said after being appointed.
The spider is "a perfect example of an incredibly clean, ruthless killer", he added.