A day after London’s popular mayor Boris Johnson stated that he is backing a British exit from the European Union, the British currency recorded its biggest drop in seven years.

Sterling experienced a more than 2 percent drop against the dollar, reaching its lowest level in seven years.

“Sterling seems to have fallen off the Boris cliff this morning,” wrote Ranko Berich, head of market analysis at Monex Europe, in a briefing note. “This could be just the start of the great Brexit Selloff of 2016.”

The country is due to vote June 23, and polls show two sides to be virtually tied.