I must admit to a certain lack of interest in the argument about whether the referendum was advisory or not. There is not the slightest doubt in law that the referendum was advisory only. Nor is there the slightest doubt that Parliament, by passing the bill to invoke article 50, exercised its sovereign rights to take that advice and make it effective in law. Of course they did not have to do this, but the essential role of Parliament is to take decisions, which it did.

It is also within the duty of Parliament to debate and potentially change its decisions when it thinks it appropriate, and it would still have that obligation even if the referendum had been legally binding.

All that is the past, and is only of relevance, really, in terms of how it affects current and future decisions. If Boris fights to stay on after a vote of no confidence, he can make the argument that it is line with the 2016 will of the people. But it one based on duty, not law. In theory anyway: in practice it is much more likely to be based on his self-interest.