a briefing paper 07212 was sent to all mps it said.. section 5 .the referendum was advisory it does not bind parliament or the government to act on it
section 6 says if there were any suggestion WHATSOEVER that there would be a change, such as leaving the EU A MAJOR CONSTITUTIONAL CHANGE would involve A CHANGE IN THE RIGHTS OF THE CITIZENS OF THE UK then a super majority would be required, this document was sent in advance of the debate in 2015.
Iwas talking about this right at the beginning, but no one took any notice