"And Nigel, the fact that Parliament was obliged to vote on whether to invoke Article 50, a vote separate from the earlier one on whether to hold a referendum, confirms that it was a separate matter from the in-out vote."
That may possibly be true but I think a more likely explanation of the mess is than a vote for out was not contemplated, and the necessary legislation to make it fly without dispute, simply did not occur. Aspects of the out vote that were not specifically addressed will be subject to dispute until(if) Brexit occurs. It does not help that the Government does not appear to give the result it's fullest support.
The departure negotiations are like watching a tadpole swimming through treacle.