https://www.bbc.co.uk/news/uk-politics-54907188

Lee Cain: Senior Johnson adviser to leave Downing Street

One of Boris Johnson's closest aides, director of communications Lee Cain, has resigned amid reports of internal tensions in Downing Street.

In a statement, he said he was leaving next month, despite having been offered the new role of No 10 chief of staff.

Mr Cain has worked with the prime minister for several years.

https://en.wikipedia.org/wiki/Lee_Cain