LONDON - Britain's next prime minister, Theresa May, called on Monday for the country to unite under her leadership, promising to make a success of negotiating the country's divorce from the European Union. After receiving official confirmation she had won a leadership contest of the ruling Conservative Party following the exit of the only other candidate, May told reporters: 'Brexit means Brexit and we are going to make a success of it ... we need to unite our country.' May is due to be installed as prime minister in succession to David Cameron on Wednesday.