The UK and the EU have reached a landmark deal which has branded a "win-win".
The PM declared that "Britain is back" after months of sometimes strained negotiations with Brussels, which carried on through the night. He urged the country to move on from "stale old debates and political fights" as he unveiled a major reset of relations with Europe, the country's biggest trading partner.
There were breakthroughs on security and defence, law enforcement, trade, and encouraging measures to tackle illegal migration. The Government also secured a deal which is expected to shorten queues for British travellers in Europe after years of misery. But compromises on fishing in British waters - more on that below - have already sparked a fierce backlash.
Speaking at a press conference alongside EU Commission President Ursula von Der Leyen and European Council President Antonio Costa, Mr Starmer said the UK would have "unprecedented" access to markets in Europe.
The Prime Minister said: "This is the first UK-EU summit, that marks a new stage in our relationship. And this deal, is a win-win. It delivers what the British public voted for last year."
Here we look at some of the key things that got agreed.
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Security and defenceWith war raging in Europe, getting agreements on security and defence could not be more important. Both sides said it is crucial to "strengthen their cooperation on security and defence".
A new Security and Defence partnership, the written deal states, will see the UK and EU work closer on supporting as well as launching new security and defence initiatives. These will include work on boosting the defence industry, space security, mobilising military personnel.
And in a big boost, work will begin to explore British access to the Security Action for Europe (Safe). This is a £150billion fund for defence projects, and the Government is desperate for UK companies to be able to bid for contracts. The Government says the agreement "paves the way" for British arms firms to be able to access SAFE.
MigrationThe Government has said the UK needs to work closer with Europe to tackle irregular migration.
Difficult relations with the EU did not help in his pledge to stop the boats. The agreement says the two parties will "deepen information sharing" - a big step after Britain lost access to key databases after .
There will also be a "whole route approach" to tackling people smuggling. This will be music to the PM's ears, as information sharing and joint co-ordination will be vital.
The UK and the EU will also work together on returns, including to "third countries" - a possible reference to returns hubs which the Government is exploring. Access to key networks such as the European Migration Network and agencies, including the Agency for Asylum and Frontex will also be stepped up.
Cooperation on visa absue will also be stepped up, with the UK and EU set to exchange analysis in order to tackle it together.
Another big boost for the Government is that co-operation will be stepped up on law enforcement.
As well as work on illegal migration, as outlined above, there will be work on wider crimefighting. The agreement says that there will enhanced cooperation and information with Europol, the European Union Agency for Law Enforcement Cooperation.
It follows concerns from law enforcement agencies that Brexit had impacted Britain's intelligence gathering and monitoring. The agreement states there is scope for "quicker, better and deeper implementation" of previous agreeements.
And crucially the two parties will explore ways to better exchange data on fingerprints, DNA, and criminal records of third country nationals. And there will also be work on setting up automated searching of vehicle registration data as well as widening the exchange of data to facial images. This is something the Government has long called for.
Access to EU electricity markertOne big breakthrough in the document is a commitment to explore the UK's participation in the EU's internal electricity market.
It says that the two parties "share the view that close cooperation on electricity is in the interest of both the European Union and the United Kingdom". The two sides agreed to explore options in detail - with current trading arrangements continuing in the meantime.
There is also an agreement to continue work together on energy technologies such as hydrogen, carbon capture, utilisation and storage and biomethane.

Another thing tackled by the document is an agreemeent to set up a Common Sanitary and Phytosanitary Area - referred to as an Sanitary and Phytosanitary (SPS) Agreement.
This would remove a lot of the certificates and controls needed when moving animals, animal products, plants, and plant products between the UK and EU. The agreement covers food safety rules. But controversially the agreement means that any disputes can be settled by the Court of Justice of the European Union - the ultimate authority for all questions of European Union law.
It says the UK should be involved at an early stage and should "contribute appropriately" to decisions. The European Commission would be required to consult with the UK on policy-making.
FishingThis has already provoked a backlash after details of the agreemenet were published. The deal will retain the existing status quo - which gives EU boats access to UK waters - until 2038. The Brexit deal, reached under , saw the UK regain 25% EU quotas, but this was set to run out next year.
The UK will carry on agreeing annual quotas with the EU and Norway. Licences will be issued to control who fishes in British waters.

The UK and the EU are set to explore a new youth mobility scheme. There is already a similar agreement in place with countries including Australia and Canada, and sees 18 to 30 year olds able to live and work overseas - and vice versa.
The agreement states that it will help young people who travel to the EU to work, study, volunteer, or simply travel, for a limited period of time. This would be a dedicated visa path, to ensure the number benefiting is "acceptable to both sides".
Work will also start on bringing the UK into the Erasmus+ programme, which supports education and training across Europe.
eGatesAnyone who has travelled into Europe since Brexit will know the misery of long queues Brits have to endure.
The deal announced today aims to deal with this. It says the UK and EU will "continue their exchanges on smooth border management". This includes the potential use of eGates where appropriate.
The agreement notes that European Union citizens can use eGates in the and that there will be no legal barriers to eGate use for British nationals traveling to and from European Union Member States.
Music toursAnother bit of good news, this time for UK musicians.
Artists have long complained that the Brexit deal made touring in Europe impossible. The new agreement looks to address that. It says it recognises the value of travel and cultural and artistic exchanges.
This includes the activities of touring artists, the document says.
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