A record 46.5 million voters have registered to decide Britain 's future in the 28-nation European Union, which was born out of a determination to unite in lasting peace after the carnage of two world wars.
Across London and southeast England, many voters braved torrential rain to have their say in a battle fought on two main fronts: immigration and the economy.
The once-in-a-generation referendum asks: "Should the United Kingdom remain a member of the European Union or leave the European Union?"
In one of the last opinion polls, "Remain" took the lead with 48 percent against "Leave" on 42 percent. The remaining voters were undecided, according to the telephone survey by ComRes for the Daily Mail and ITV News.