Geordie Greig is to be the new editor of the Daily Mail, putting a staunch remainer in charge of one of the most pro-Brexit newspapers in the country.

The current Mail on Sunday boss will replace Paul Dacre, 69, who is stepping down in November.

Lord Rothermere, who controls the two papers, said: “Geordie has been an outstanding editor of the Mail on Sunday, and I am delighted that he will continue the high-quality journalism that Paul has made a hallmark of the Daily Mail for more than 25 years.”

A source with knowledge of the discussions saido that Greig’s appointment was part of a process of “detoxifying the Daily Mail” after Dacre’s editorship.

Any change to the Daily Mail’s editorial line on Brexit could have substantial implications for the government.

Under Dacre’s leadership, the paper has launched ferocious front-page attacks on public figures who it deems to have challenged the decision to leave the EU.

One labelled high court judges “enemies of the people”, another urged Theresa May to “crush the saboteurs” with an early election, and a recent attack on the House of Lords described them as “dinosaurs in ermine”.

The paper is regularly the focus of morning news meetings in Downing Street, while Dacre was an early and consistent backer of May’s policies.

Greig, 57, however, has repeatedly clashed with Dacre during his stint at the Mail on Sunday. Staff at both papers expressed surprise at the idea the two editors would be able to work together during the transition period, saying there was no love lost between them.

The sister news outlets frequently battled during the Brexit campaign, and Greig’s Mail on Sunday has often gone out of its way to rubbish the daily paper’s scoops.

Under the new arrangement, according to a company insider, it is expected the two papers will work much closer together, which could result in cost savings and opens the door to potential job cuts.

Greig has been in his current position since 2012, having previously edited the London Evening Standard and Tatler magazine. Ted Verity, the deputy editor of the Daily Mail, will take control of the Sunday edition.

Greig will have three challenges as Daily Mail editor: keeping the newspaper influential among politicians; ensuring it continues to make money in the face of declining circulation; and stepping out of the shadow of a man who has held the job for a quarter of a century.

Dacre’s commitment to the job will be hard to match, according to Adrian Addison, the author of the book Mail Men, an unauthorised history of the newspaper.

“He’s a tyrant. He’s a bully. He’s hands-on,” Addison said. “When he first became editor, he would get so wound up near edition time he used to behave like a gorilla and scratch himself so hard that his back would bleed. The blood would come through his shirt. That’s the wound-up tension.”

Addison insists that Dacre – one of the most divisive individuals in the newspaper industry – has an impressive understanding of his audience.

“He has a natural affinity with the lower middle-class reader. He doesn’t communicate with many members of the public – everything is purely gut instinct and surrounding himself with people who he listens to.”

The financial analyst Ian Whittaker, who covers the fortunes of the papers’ parent company DMGT for Liberum Capital, warned against too much change.

“From their standpoint, they probably want to keep the formula of a winning product, so I wouldn’t expect that much change in terms of direction of the Mail.”

Whittaker speculated that giving the job to Greig could constitute a risk to the Daily Mail’s income unless the editor was willing to compromise on his political views.

“You don’t want what happened to the Express 20 years ago,” said Whittaker, referring to when the Mail and the Express were locked in a battle for readers. “The Express decided to support Tony Blair, it annoyed its readership, and its circulation took a hit.”

Greig, however, has form for bold gestures. When the old Etonian took over the Evening Standard in 2009, he issued a series of advertisements saying “sorry” to Londoners for the previous editor’s coverage.

Behind the scenes, there is much discussion of the role played by the Rothermere family, who have a controlling interest in DMGT, especially the current owner’s wife, Lady Rothermere.

It has been suggested the Daily Mail’s relentless pro-Brexit stance has become increasingly problematic among their social circle in Wiltshire, where they built a modern country house and mix with the likes of the fashion designer Jasper Conran.

“[Greig] was parachuted in by Rothermere because he’s very good friends with Lady Rothermere – he’s a courtier,” claimed Addison.

Greig will inherit a highly profitable print outfit which, together with its Sunday counterpart, delivered income of £219m during the first six months of 2018, despite the Daily Mail’s circulation almost halving over the last 15 years, to sit at 1.3m copies a day. 

By comparison, MailOnline, which claims to be the biggest English-language news website in the world with tens of millions of readers, brought in just £61m during the same period, albeit with a smaller cost base. Despite enormous success in the US under the editor Martin Clarke, the site recently reported a fall in traffic, which it blamed in part on changes to Facebook’s algorithm.

Daily Mail insiders played down the possibility that the print edition, which until now has fiercely guarded its identity, could merge with the celebrity-obsessed MailOnline website in the near future, although there is the possibility that they could work together more closely. 

“I wouldn’t work on the assumption there are necessarily massive changes planned,” said one source.

“But at the same time that doesn’t mean they won’t happen, because once new people are appointed they may decide there are things they want to do.”