British Prime Minister Boris Johnson, European Commission President Ursula von der Leyen and European Council President Charles Michel signed the divorce deal for Britain to leave the EU on Friday.

Johnson hailed the signing, one of the final steps required before Britain begins the formal process of leaving the European Union on January 31, as a “fantastic moment.”

Johnson tweeted that the agreement “honours the democratic mandate of the British people,” who voted for Brexit by a majority of 52 per cent in a 2016 referendum.

“This signature heralds a new chapter in our nation’s history,” he wrote.

In a Downing Street statement, Johnson said:

“The signing of the withdrawal agreement is a fantastic moment, which finally delivers the result of the 2016 referendum and brings to an end far too many years of argument and division.”

The agreement was transported from Brussels to London after von der Leyen and Michel had signed it.

The signing of the agreement “opens the way for its ratification by the European Parliament,” von der Leyen tweeted.

The parliament is due to cast its final vote on the withdrawal agreement next Wednesday, and is expected to pass the deal. As a final step, it then requires the formal adoption of the remaining 27 EU member states.

Under the deal, Britain will leave the European Union at midnight (2300 GMT) on January 31. A transition period then kicks in, until at least December 31, 2020, giving the two sides time to negotiate their future relationship.

The EU’s diplomatic corps also appointed its future ambassador to Britain on Friday, choosing Portugal’s Joao Vale de Almeida, who until recently served as the bloc’s emissary to the United Nations.

Michel Barnier is to remain Brussels’ main messenger on all things Brexit, however, staying put in his role as chief negotiator. He is set to receive his mandate for negotiations on the future relationship in the coming weeks.

The two sides have a small window to thrash out a trade agreement, but also new arrangements covering fisheries, financial services access and the sharing of data important for security, among other issues, by the end of the year.

“Things will inevitably change but our friendship will remain. We start a new chapter as partners and allies,” Michel tweeted on Friday.

The British parliament has already ratified the Brexit withdrawal deal, and Queen Elizabeth II has also given royal assent.

The legal text runs to more than 500 pages and specifies the details of Britain’s departure, including key provisions on citizens’ rights, arrangements to maintain the peace along Ireland’s land border with the United Kingdom and Britain’s remaining financial obligations.