The amendment says, “nothing … prevents”, which I suppose could be said to be saying that the royal prerogative exists—so to that extent it is unnecessary—but it restricts what the Prime Minister can do in its final words. That is my answer to my noble and learned friend.
The wise words of the noble Lord, Lord Norton of Louth, at Second Reading about the constitution are particularly relevant in this context. One of the repeated observations from the EU is that it wants to know what the UK wants. In the context of this Bill, it will ask the reasons for the extension. What answer is the Prime Minister supposed to give, acting as an agent for this disunited Parliament?
This amendment is a worthwhile attempt to clarify the mandate, which apparently the Prime Minister has by virtue of this Bill, but I doubt it is necessary, for the reasons I have given, and I suggest that the House thinks long and hard before making such an important change.