BBCWes Streeting has quit as health secretary after days of speculation that he is preparing to mount a leadership challenge to Sir Keir Starmer.The now ex-health secretary is brutal in his assessment of Sir Keir's leadership of the Labour Party and the country in his resignation letter.But he stops short of announcing a leadership challenge, saying instead that the prime minister should take steps to ensure there is a "broad" contest to replace him with "the best possible field of candidates".Here are four key excerpts from the near-1,000 word letter and what they may mean.'Dishonourable' to remain in postStreeting delivers the killer blow, saying he has "lost confidence" in the prime minister but also makes clear that his decision to quit on a matter of principle has nothing to do with policy differences and everything to do with Sir Keir's leadership of the Labour Party and the country.'Nationalists are in power in every corner of the UK'