// I thought it was written in law that we leave, with or without a deal, on the 31st October. //
If this Bill becomes law, then it forces the PM to present a deal to Parliament, and if he can't present that deal or if Parliament rejects it, then he needs to ask for an extension . So the date of 31st October would then, subject to the EU's consent, be postponed. As happened the last two times we requested an extension, then the Prime Minister, or Secretary of State for Exiting the EU, would lay the necessary Statutory Instruments to amend specific references to the Date in the EU (Withdrawal) Act 2018, so 31st October would disappear and be replaced with 31st January (or whatever other date ends up being agreed on).