Fixed-term Parliaments Bill

The noble Lord is of course a very clever lawyer, so perhaps he could just explain to the House, for the purposes of clarification, how he considers supporting an amendment that says that each Parliament, after each general election, should meet to consider how long the Parliament should last, is compatible with the Labour Party manifesto commitment a year ago, which said that if the party returned to government, it would legislate for fixed-term Parliaments?