The British pound crossed the symbolic threshold of $1.40 Friday, driven by a rapid vaccination campaign in the United Kingdom and the year-end trade deal between Britain and the European Union.

At around 09:30 GMT, the British currency recorded 1.4008 against the dollar, a level it has not reached since the end of April 2018.

"There was no information Friday to explain the pound's outperformance, but the data remained as they had been since the beginning of the year: There were no serious consequences for Britain's exit from the European Union, while the vaccination campaign was taking place at a rapid pace, and satisfactory growth was recorded at the end," said Stephen Innes, an analyst. 

Since Dec. 24 and the last-minute trade agreement was concluded, the pound has appreciated by 3.7 percent against the dollar and 4.1 percent against the euro.

"This is an important threshold because it is the highest level of the British pound since the Brexit referendum," which was held in 2016 and led to the depreciation of the British currency, said Lee Hardman, an analyst at MUFG.