British government's Brexit bill became law after Queen Elizabeth II gave it her royal assent, paving the way for Britain's exit from the European Union (EU) on Jan 31.
Tory MPs cheered the deputy speaker Nigel Evans as he on Thursday confirmed in the House of Commons that there was now a European Union (Withdrawal Agreement) Act, the Guardian reported.
Johnson finally succeeded in getting his bill through the Commons (lower house) and the Lords after several failed attempts by his predecessor Theresa May. The journey of the bill became smoother after Boris Johnson's landslide victory in a snap general election in December.
He was not in the Commons to hear the news, but said the moment was a significant milestone. ''At times it felt like we would never cross the Brexit finish line, but we've done it,'' he said.
Armed with a 80-seat majority in the House of Commons , the bill was able to beat all opposition and passed its final legislative stage in the House of Lords (upper house) on Wednesday after peers gave it their approval.
Spelling out arrangements for Britain's departure from the union, the approved bill will be signed at a ceremony in Brussels on Friday by Ursula von der Leyen, president of the European Commission, and Charles Michel, president of the European Council.
Negotiations between Britain and the EU will soon start on a future trade deal. Johnson has repeatedly insisted that he will not extend the transition period.
Last month, the House of Commons passed his Brexit bill, where he added a clause to rule out any extension beyond Dec 31, 2020.