ITV News' Robert Peston explains how the eventful day in British politics played out.
Liz Truss has made her first prime ministerial address to the nation as she enters No 10 with one of the most challenging in-trays faced by any British peacetime leader.
The new PM raced against the clock to make it to Downing Street for her inaugural speech as the heavens opened up, a foreboding of the difficulties she will face in her first months in office.
When she finally arrived, she assured the nation and broadcasters huddled under umbrellas that "we can ride out the storm" as she outlined her vision to tackle the soaring cost of living crisis.
"As strong as the storm may be, I know that the British people are stronger," she said, as husband Hugh O'Leary stood near the door of No 10.
“I’m confident that together we can ride out the storm, we can rebuild our economy and we can become the modern brilliant Britain that I know we can be.
“This is our vital mission to ensure opportunity and prosperity for all people and future generations. I’m determined to deliver."
She talked of three priorities that she will focus on during her premiership - growing the economy, dealing "hands-on" with the energy crisis, and working on the record NHS backlog.
“I will take action this week to deal with energy bills and to secure our future energy supply," Ms Truss vowed.
Shortly after making her address Ms Truss held her first interaction with a foreign leader, speaking with Ukraine President Volodymyr Zelenskyy.
In a tweet Mr Zelenskyy said he invited the prime minister to Ukraine and thanked the British people "for the major defence & economic aid for Ukraine".
"We discussed the participation of Britain in the recovery of Ukraine. Coordinated further pressure on the RF. The goal is to stop the aggression & bring the perpetrators to justice," he said.
Later this week Ms Truss is expected to announce the details of a cost of living support package, but she is reportedly drawing up plans for a freeze in bills which could cost around £100 billion.
She vowed to grow the economy through reform and tax cuts to "reward hard work" - a comment likely included to smooth over comments she made in the campaign saying Britons "need more graft".
Turning her attention to record waiting lists and staff shortages in the NHS and social care, she pledged it would be one of the first issues her government would address.
“I will make sure that people can get doctor’s appointments and the NHS services they need. We will put our health service on a firm footing," she said.
“By delivering on the economy, on energy and on the NHS, we will put our nation on the path to long-term success.”
Continuing with her pledges, she said "we will get spades in the ground to make sure people are not facing unaffordable energy bills" and to build "hospitals, schools, roads, and broadband".
The UK's third ever female PM was formally invited to form a government in an audience with the Queen at Balmoral Castle earlier on Tuesday.
Ms Truss and her predecessor Boris Johnson flew on separate jets to meet the Queen in Scotland, where the outgoing PM handed in his resignation.
Before he left Downing Street, Mr Johnson used his speech to call for unity in the Tory party as he pledged his "fervent support" for Ms Truss during a "tough time" ahead for the country.
But he hinted that the nation has not seen the last of him in a top political job, as he compared himself to Cincinnatus, an Ancient Roman leader who is said to have returned from retirement to serve as dictator at a time of crisis.
Ms Truss again paid a glowing tribute to her predecessor Mr Johnson and said "history will see him as a hugely consequential prime minister" for delivering Brexit, the Covid vaccine and standing up to "Russian aggression".
“I’m honoured to take on this responsibility at a vital time for our country," she said.
Meanwhile, the president of the US - a key and long-term ally of the UK - is scheduled to speak with Ms Truss on Tuesday night to deepen the nations' "special relationship".
Joe Biden congratulated her, saying: "I look forward to deepening the special relationship between our countries and working in close co-operation on global challenges, including continued support for Ukraine as it defends itself against Russian aggression."
Ms Truss will not enjoy the usual "honeymoon" period of life in No 10 as she's under mounting pressure to hit the ground running to tackle one of the worst economic crises the country has seen in decades.
On Wednesday morning she will meet with her new look cabinet for the first time, having positioned a number of key allies on the front bench.
Her close confident, Therese Coffey, has been promoted to deputy prime minister and health secretary, while Kwasi Kwarteng has accepted an offer to become Ms Truss' chancellor.
At noon she will then travel to the House of Commons and meet Labour leader Sir Keir Starmer for her first session of Prime Minister's Questions.
She will face a grilling from MPs over how she intends to support households and businesses this winter.
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