No 10 frontrunner wrote ‘pro-European letter’ to Tory peer’s widow a year before campaigning for leave

Boris Johnson revealed his support for the European Union’s single market in “a pro-European” letter written the year before he decided to campaign for leave, it has emerged.

The likely prime minister’s pro-EU market sympathies were said to be revealed in a letter of condolence to the wife of the late Tory politician Sir Leon Brittan, who died in January 2015.