Boris Johnson , ex-London mayor and de facto leader of campaign for United Kingdom  exit from the European has launched an appeal for unity and attempted to draw a line under a bitterly divisive European Union referendum campaign hours after Britons voted to leave the EU.

The former London Mayor also said on Friday that the UK had  a “glorious opportunity” to re-establish itself on the world stage and “can find our voice in the world again”.

Just a year ago, Mr. Johnson was a crucial weapon for the Conservatives in the general election that gave the party full control of the U.K. government and Mr. Cameron a second term as prime minister.  He scored a major victory and is now a leading candidate to succeed Prime Minister David Cameron, who led the losing camp.

In a statesmanlike speech, flanked by Labour’s Gisela Stuart and the Conservatives’ Michael Gove, Mr Johnson said the result was a huge opportunity for the UK.

Directly addressing the millions of voters who backed Remain, Mr Johnson insisted that the result did not represent a retreat into isolationism and that Britain would remain a “great European power”.

He said: “I want to speak to the millions of people who did not vote for this outcome especially young people who may feel that this decision in some way involves pulling up the drawbridge or any kind of isolationism. I think the very opposite is true.

“To those who may be anxious at home or abroad this does not mean that that he UK will be in anyway less united nor indeed does it mean that it will be any less European.”

He said: “We cannot turn our backs on Europe. We are part of Europe. Our children and grandchildren will continue to have a wonderful future as Europeans travelling to the continent, understanding the languages and cultures that make up of common European civilisation.

“But there is simply no need in the 21st century to be part of a federal system of government based in Brussels that is imitated nowhere else on earth. It was a noble idea for its time but it is no longer right for this country.

“It is the essence of our case that young people in this country can look forward to a more secure and more prosperous future if we take back the democratic control that is the basis of our economic prosperity.”

An emotional Mr Cameron fought back the tears this morning as he announced his resignation.

Flanked by wife Samantha as he delivered an emotional statement outside Number 10, Mr Cameron said he accepted the decision of the electorate, which voted by 52 per cent to 48 per cent to leave the EU.

With a voice trembling with emotion, Mr Cameron announced he was standing down, before adding: “I will do everything I can in future to help this great country succeed.”

“I think the country requires fresh leadership. I do not think I can be the captain to take the country to its next destination.”

David Cameron’s voice broke as he finished his speech, watched on by his wife Samantha