The triggering of Article 50 has dominated newspaper headlines on Thursday.
Many papers focused on a possible veiled threat by Theresa May in which she appeared to warn European leaders that failure to reach a comprehensive Brexit agreement would result in a weakening of co-operation on crime and security, triggering accusations her remarks amounted to blackmail.
However, speaking to the BBC's Newsnight, Work and Pensions Secretary Damian Green said it was a misunderstanding and the the two issues had been mentioned side by side because they were "all bound up in our membership of the European Union".
The Guardian led with the headline "Eu warns: don't blackmail us", referring to Ms May's comments in the letter which triggered Article 50 which appeared to warn that failure to reach a comprehensive Brexit agreement would result in a weakening of co-operation on crime and security, triggering accusations her remarks amounted to blackmail.
The Daily Mail likewise noted that the EU warned the Prime Minister not to "blackmail" it.
The newspaper struck a more optimistic tone with its headline "cheers to a great British future!", accompanied by an image of Nigel Farage celebrating the beginning of the UK's Brexit journey.
The Daily Mirror also focused on Ms May's "security threat" if a Brexit agreement was not reached.
It also noted that German Chancellor Angela Merkel had rejected the Prime Minister's calls for early talks on the single market.
The Daily Record branded the Prime Minister "despicable", noting that her comments on security cooperation came just one week after the Westminster terror attack.
The Times too focused on Theresa May's "threat" to the "terror pact" between EU member states, and noted that the triggering of Article 50 spelt the "end of the beginning for both sides".
Along with The Times, the Metro led with the picture of Sir Tim Barrow handing the letter which triggers Article 50 to European Council President Donald Tusk.
Their play on the French for goodbye "adieu" focused on the UK leaving the EU rather than on Ms May's perceived security threat, although this was bullet pointed underneath the headline, along with Ms Merkel's rejection of early trade talks.
The i also used an image of the formal handing over of the letter, accompanied by the word "goodbye" in numerous different European languages.
Unlike other newspapers, the i did not give prominence to Ms May's perceived threat over security, instead referring to a "rift" having already been created.
The Daily Telegraph's headline called the beginning of Britain's Brexit journey "a magnificent moment" and spoke of the "jubilation" as Article 50 was formally served.
Foreign Secretary Boris Johnson also had a front page article in which he called for the country to "back Britain and go global".
The Financial Times' lead image did not contain Sir Tim Barrow, only Mr Tusk with the letter which triggered Brexit.
The FT also focused on Mr Tusk's speech for its headline "thank you and goodbye", while giving the Prime Minister's perceived threat over security equal prominence to other issues.
The Sun's headline was the highwayman's phrase "your money or your lives", writing that Ms May was offering the UK's skills on fighting terror in return for a free trade deal.
Rather than a picture of the Article 50 letter being handed to Mr Tusk, the newspaper used an image from the funeral of singer George Michael which took place on Wednesday.
The Daily Star was the only national newspaper not to lead on Brexit, instead focusing on the funeral of singer George Michael.
Nor did its front page mention Ms May's apparent security threat, instead focusing on Mr Tusk's emotional message to the UK in which he said "we already miss you".