The United Kingdom and the European Union have agreed on a post-Brexit trade deal after months of torturous negotiations, averting the prospect of a chaotic and acrimonious divorce at the end of this year.

The deal, announced on Thursday, came just one week before the UK is due to exit the EU’s single market and customs union on December 31.

“The deal is done,” UK Prime Minister Boris Johnson tweeted, as he posted a photo of himself with both thumbs raised in celebration.

Delivering a televised address, Johnson hailed striking what he called “the biggest trade deal yet”, adding that the UK had taken back control of its laws, borders, and fishing waters.

“We have completed the biggest trade deal yet, worth 660 billion pounds a year, a comprehensive Canada-style free trade deal between the UK and the EU,” he said.