Boris Johnson has urged world leaders not to "repeat the mistake" of the 2008 financial crisis as they met for talks on how to recover from the coronavirus pandemic.
In one of the most high-profile moments of his premiership so far, the prime minister has welcomed G7 leaders to Cornwall for a seaside summit.
Mr Johnson has been joined at Carbis Bay by US President Joe Biden, Canada's Justin Trudeau, Japan's Yoshihide Suga, Germany's Angela Merkel, France's Emmanuel Macron, Italy's Mario Draghi, and EU presidents Ursula von der Leyen and Charles Michel.
It is the first in-person G7 summit for nearly two years and the prime minister told his fellow leaders it was "genuinely wonderful" to see them all in person after the "most wretched pandemic our countries have faced for our lifetimes, maybe longer".
Ahead of three days of talks, Mr Johnson urged the G7 to "learn the lessons" from the COVID crisis after the "doubtelss" errors that had been made, and to "make sure we now allow our economies to recover".
"I think they have the potential to bounce back very strongly and there's all sorts of reasons for being optimistic," he added.
"But it is vital we don't repeat the mistake of the last great crisis, the last great economic recession in 2008, when the recovery was not uniform across all parts of society.
"I think what's gone wrong with this pandemic, or what risks being a lasting scar is, I think, that the inequalities may be entrenched.
"We need to make sure that as we recover, we level up across our societies and we build back better."
As he sat down with his fellow leaders, Mr Johnson said the G7 was "united in our vision for a cleaner, greener world".
And he called for the world's leading democracies to focus on "building back greener and building back fairer and building back more equal - in a more gender neutral and, perhaps, a more feminine way".
This weekend's summit will see world leaders enjoy some downtime during their stay in Cornwall - including a beach BBQ and toasted marshmallows over fire pits - but Mr Johnson has made securing agreements on COVID vaccines, future pandemic preparedness, the environment and girls' education his ambition for the talks.
The prime minister will also be keen to sidestep any fresh turmoil over lingering Brexit disputes.
Mr Johnson wants this weekend to see G7 nations commit to providing one billion doses of COVID vaccines to developing countries as part of a bid to vaccinate the entire world by the end of next year.
The UK has committed to providing at least 100 million doses, while Mr Biden has said the US will purchase 500 million doses of the Pfizer jab to donate to poorer countries.
The prime minister also has ambitions for a new global pandemic surveillance network, as well as an effort to accelerate the development of vaccines, treatments and tests for any new virus from 300 to 100 days.
Australia's Scott Morrison, South Africa's Cyril Ramaphosa and South Korea's Moon Jae-in will join the G7 talks as summit guests on Saturday, while India's Narendra Modi will join discussions via video link.
Mr Johnson also wants the weekend to see G7 leaders commit to tackling the "moral outrage" of millions of girls around the world being denied an education.
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The prime minister is set to hold talks with the EU's Ms von der Leyen and Mr Michel on the sidelines of the summit, with the UK and the bloc remaining at a stand-off over the implementation of the Northern Ireland Protocol.
Ahead of the official start of the G7 summit, French President Emmanuel Macron pointedly shared an image of himself, Mrs Merkel, Mr Draghi and the two EU presidents sat at a table together.
"As always, the same union, the same determination to act, the same enthusiasm! The G7 can begin," Mr Macron posted on Twitter.
On Thursday, Mr Johnson said he and Mr Biden were in "complete harmony" over Northern Ireland, despite earlier reports the US had lodged a formal diplomatic protest with the UK over the dispute.
Ahead of the UK hosting the COP26 climate change summit later this year, environmental issues will also be a large part of discussions over the weekend.
Prince Charles is hosting a reception on Friday for the G7 leaders and CEOs of some of the world's largest companies to discuss how the private sector can work with governments to tackle the climate emergency.
And Sunday's final talks will see leaders addressed via a pre-recorded video from Sir David Attenborough.
The prime minister wants G7 nations to promise to halve their carbon emissions by 2030, in order to limit the rise in global temperatures to 1.5 degrees.