STAFFORD, ENGLAND - MAY 17:  The Vote Leave campaign bus arrives at  JBMI Group, Kingsilver Refinery in Hixon, Staffordshire during the Vote Leave, Brexit Battle Bus tour on May 17, 20016 in Stafford, England. Boris Johnson and the Vote Leave campaign are touring the UK in their Brexit Battle Bus. The campaign is hoping to persuade voters to back leaving the European Union in the Referendum on the 23rd June 2016.  (Photo by Christopher Furlong/Getty Images)