Prime Minister Boris Johnson says he will prove 'doomsters' wrong on Brexit in Downing Street speech

• Boris Johnson delivers his first speech as Britain's new prime minister.
• His words are almost drowned out by protesters at the end of the speech.
• He delivers a combative address attacking the "doomsters" who predict he will fail to take Britain out of the EU.
• Visit Business Insider's home page for more stories.

Boris Johnson has promised to prove the "doomsters" and "gloomsters" wrong and deliver Brexit by the end of October, in a combative first speech as Prime Minister, delivered from the steps of Downing Street.

Johnson promised to take Britain out of the EU on October 31, with or without a deal, and attacked the "pessimists" who predict that he will be forced to seek another delay to Britain's exit.

His speech was almost drowned out by the sound of protesters gathered at the end of Downing Street.

Watch Boris Johnson's first Downing Street speech

Read more: Boris Johnson is the new prime minister of the United Kingdom

Read more: A human chain of protesters stopped Boris Johnson's car as he went to meet the Queen