Boris Johnson will today unveil a “Cabinet for modern Britain” as he begins his first day as Prime Minister.

The new PM is set to welcome a record number of ethnic minority politicians to his top team and increase the number of women attending as full Cabinet members.

It is believed Priti Patel, the former international development secretary, will make a return to Cabinet – possibly as Home Secretary – and Employment Minister Alok Sharma is also expected to be promoted to Mr Johnson’s new-look team.

Jeremy Hunt, who hoped to keep his job as Foreign Secretary, was reportedly offered the post of Defence Secretary but turned it down.

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Mr Hunt said the new Tory leader would be “a great PM for our country at this critical moment”.

The reshuffle is set to propel a number of Tory rising stars with promotions likely for members of Mr Johnson’s transition team: Oliver Dowden, a junior minister at the Cabinet Office, who was David Cameron’s deputy chief of staff, and Rishi Sunak, the Local Government Minister.

A source close to Mr Johnson said: “Boris will build a Cabinet showcasing all the talents within the party that truly reflect modern Britain.”

An early and surprise appointment is long-serving whip Mark Spencer, who becomes Chief Whip. The relatively unknown Nottinghamshire MP has been given a crucial role given the Johnson Government could soon have no working majority.

It is also understood Mr Johnson has hired the Sky TV executive, Andrew Griffith, to be his chief business adviser. Mr Griffith loaned the Tory leader his £9.5 million Westminster townhouse from where he ran his campaign.

However, before the new leader formally takes over from Theresa May several Cabinet ministers will resign, including Philip Hammond, David Gauke and Rory Stewart, all of whom have pre-announced their departures because they cannot sign up to Mr Johnson’s so-called “no-deal loyalty pledge”.

Before the leadership result was announced, Anne Milton, the Education Minister, stood down, expressing "grave concerns" about a no-deal Brexit.

At the QEII conference centre, opposite the Houses of Parliament, a gathering of Tory MPs, peers and journalists heard that Mr Johnson had secured 92,153 votes - 66.4 per cent - to defeat his rival Jeremy Hunt, who was backed by 46,656 Tory members - 33.6 per cent.

Ardent Brexiteer Jacob Rees-Mogg declared that the new leader had received a “clear mandate to deliver Brexit and unite the country".

Mr Johnson used his victory speech to promise he would "energise the country" and meet the October 31 Brexit deadline with a "new spirit of can-do".

The Herald: Camley's cartoon: Boris Johnson becomes Prime MinisterCamley's cartoon: Boris Johnson becomes Prime Minister

Mr Johnson told his colleagues: “Like some slumbering giant, we are going to rise and ping off the guy ropes of self-doubt and negativity with better education, better infrastructure, more police, fantastic full-fibre broadband sprouting in every household. We are going to unite this amazing country and we are going to take it forward."

Mr Hunt, who hopes to keep his job as Foreign Secretary, said the new Tory leader would be "a great PM for our country at this critical moment".

Earlier, Mrs May chaired her last Cabinet at the end of which she was presented with a black handbag from Liberty and a Lalique necklace.

Her spokesman said David Lidington, the PM’s de facto deputy, thanked her on behalf of the Cabinet for her “great dedication to public service and her commitment to the Union".

A Downing St source said: "It was a genuinely nice ending."

Today, Mrs May will take her final PMQs before returning to Downing St, where she will thank staff and then give a final address from behind a lectern.

The PM will then be driven to Buckingham Palace to offer her resignation to the Queen. Moments later, Mr Johnson will arrive to be invited by Her Majesty to form a new government.

Following the audience, the new PM will be driven to Downing St, where he will make his first keynote speech before going inside to meet the No 10 staff and begin the process of putting a government together.

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Some if not most Cabinet appointments are expected on Wednesday evening. The following 48 hours will see Mr Johnson appoint junior ministers.

It is expected he will make a Commons statement on Thursday before Westminster rises for its summer recess in the evening.

Mr Johnson will then spend the first few days getting to grips with the long list of issues in his in-tray; not least Brexit, the crisis in the Gulf, rekindling UK-US relations and bolstering the Union.

These priorities are expected to involve the PM travelling to Brussels, Scotland and Washington.

After visiting Tory headquarters, Mr Johnson “love-bombed” the 1922 backbench committee.

Outside Committee Room 14 in the Commons, loud cheers and laughter were heard as the new party leader addressed colleagues.

Tory backbencher Keith Simpson, emerging early from the meeting, declared: “The circus has come to town. I couldn’t stand any more of it.”

He added: “They were all sitting in the body of the kirk trying to look as though they are not ambitious little s**ts.”

Colin Clark, the MP for Gordon, told The Herald: “Finally, we’ve got a positive leader. People are fed up with Nicola Sturgeon’s miserable negativity and the grievance culture of the SNP. They want some positivity.”

Nicky Morgan, the former Education Secretary, said it was “vintage Boris...serious and entertaining” while Steve Baker, the Brexiteer and former Brexit minister, said Mr Johnson’s speech was “good, strong, solid stuff to bring the party back together”.

Elsewhere, Labour leader Jeremy Corbyn urged Mr Johnson to call a general election and promised to table a motion of no confidence in the new PM "when it is appropriate to do so" and "at a time of our choosing".

Jo Swinson, the new Liberal Democrat leader, said: “Whether it is throwing people under the bus or writing a lie on the side of one: Britain deserves better than Boris Johnson.”

First Minister Nicola Sturgeon expressed "profound concerns" about a Johnson premiership and called for Scotland to be given the right to determine its own future.