Britain Prepares for Historic EU Referendum

Ballot boxes to be used for voting in the European Union referendum, wait to be collected from storage in New Parliament House for delivery to polling stations in Edinburgh, in Scotland on June 22.

A man voices his opinion on the referendum during a "Gibraltar stronger in Europe" campaign event in the British overseas territory Gibraltar, Spain on June 16.

Two activists with the EU flag and Union Jack painted on their faces kiss each other in front of Brandenburg Gate to protest against the British exit from the European Union, in Berlin, June 19.

Local council leaders hold placards during a Vote Remain event at Manchester Metropolitan University's student Union in Manchester, northern England on June 16.

A woman reads a newspaper on the underground in London with a "vote remain" advertisement for the EU referendum, June 22.

Tributes in memory of murdered Labour Party MP Jo Cox, who was shot dead in West Yorkshire, are left at Parliament Square in London.

Jeremy Corbyn, the leader of Britain's opposition Labour Party, arrives at a Vote Remain event in Manchester, June 21.

Leader of the United Kingdom Independence Party (UKIP) Nigel Farage speaks to media after a launch for an EU referendum poster in London on June 16.

Britain's Prime Minister David Cameron speaks at a "Stronger In" campaign rally at a school in Witney, southern England, May 14.

Royal Ascot attendees show off their EU referendum inspired costumes at the races on June 14, in Ascot, England.

Gallery: Hats and Horses: Ladies Flaunt Fashion at Royal Ascot

Former London Mayor Boris Johnson holds up a Cornish pasty during the launch of the Vote Leave bus campaign, in favor of Britain leaving the European Union, in Truro, Britain on May 11.

Musician and campaigner Bob Geldof (center) joins a counter demonstration as a flotilla of fishing vessels campaigning to leave the European Union sails up the river Thames in London, June 15.

A girl runs past a Vote Leave sign, protruding from the garden of a house in Altrincham, northern England, May 2.