I have long said that in the current situation the Prime Minister can force a No Deal Brexit if he or she wants, regardless of what Parliament thinks. In this I differ from many commentators who insist that this is impossible because Parliament can stop it. This short article from the Institute of Government agrees with me:
Several Conservative leadership candidates are clear that they prefer leaving the EU without a deal to leaving with Theresa May’s deal – or not leaving at all. If one were to becomes Prime Minister, then MPs who oppose a no deal Brexit will need a way to block or delay such an outcome.
But unless the Speaker chooses to be even more flexible in his interpretation of parliamentary convention, MPs have limited options.