Illegal Migration Bill

That is correct: the ECHR memorandum is one of the documents prepared to support the Bill in its passage through Parliament. Obviously, if a matter of interpretation were required, it is the sort of material that those looking for an interpretation might be minded to refer to. Indeed, it is open to those in Parliament to refer to such documents. It is, of course, right to say that the ECHR memorandum is a standard part of the package in relation to public Bills—so, in that sense, it has regular status.