Boris Johnson is now officially Britain's prime minister.

Johnson left Buckingham Palace after being appointed by Queen Elizabeth II. The palace confirmed that Johnson had been appointed "as Prime Minister and First Lord of the Treasury," another of the British leader's titles.

During his first speech as Prime Minister, Johnson vowed that the U.K. will leave the European Union on Oct. 31 - "no ifs, ands or buts."                 

Johnson sought to persuade the public to back him - saying that the time has come to act on the nation's departure from the European Union.

In his first speech as leader outside 10 Downing Street, Johnson says "he will get 'a new deal, a better deal' from the EU on Brexit.

He added that while there will be difficulties, much of the nation's confidence has been sapped by the refusal to take action.

Earlier he visited the palace to meet with the monarch Wednesday after predecessor Theresa May resigned, failing to secure parliamentary approval for her deal to leave the European Union.

Johnson defeated his rival Jeremy Hunt overwhelmingly in a vote of Conservative Party members.

The victory is a triumph for the 55-year-old Johnson, an ambitious but erratic politician whose political career has veered between periods in high office and spells on the sidelines.

Johnson has vowed that Britain will quit the European Union, "come what may," on the scheduled Brexit departure date of Oct. 31 even if it means leaving without a divorce deal.

But he faces a rocky ride from a Parliament determined to prevent him from taking the U.K. out of the bloc without a withdrawal agreement. (AP)Â