Writing exclusively for Comment Central, Professor Alex de Ruyter and David Hearne from Birmingham City University's Centre for Brexit Studies provide their latest expert analysis on the road leading up to, and options after, 29 March 2019.

The Government's 11th hour delay of the parliamentary vote on the proposed Withdrawal Agreement suggests that the vote was set to be lost by an enormous margin. After all, it was widely touted that if the loss were to be narrow then Theresa May would be able to use this to make some changes at the margins to reassure waverers and attempt another parliamentary vote. The fact that the vote was postponed indicates that any defeat was going to be utterly resounding. So what happens now?

The PM's announcement that the 'meaningful vote' on the Withdrawal Agreement is set to occur during the week of 14th January 2019 is, on one level, not a surprise. It was always unlikely that Theresa May would reverse course and hold a vote before the House of Commons rises on 20th December. Given that the House does not return until 7th January, a further debate could push the final vote into the next week. However, this is uncomfortably close to the legal deadline of 21st January for the Government to put forward a response to the House of Commons .

There will probably be further attempts to renegotiate parts of the "backstop" on Northern Ireland. This is likely to prove challenging as the stated view of the EU is that the Withdrawal Agreement is final. Nevertheless, it is clear that there is little appetite within the EU for a disruptive no-deal Brexit. Ultimately, however, most of the EU can afford to walk away without a deal as, outside of Ireland, no other member is nearly as exposed to Brexit as the UK.

This then leads to the question of what might conceivably be changed. An explicit time-limit of the form allegedly desired by the PM is unlikely to be acceptable ? a backstop that expires is surely no backstop at all.

Nevertheless, it might be possible to develop an arbitration mechanism that would assuage some MPs' fears of becoming "trapped" inside the backstop.

The Withdrawal Agreement might also be amended such that the backstop made explicit reference to some kind of independently proven technological solutions. This might mollify Conservative Brexiteers, although one would imagine that the EU would want to maintain say over what precisely would constitute sufficiently well proven solutions. No such technologies have yet been proven to the satisfaction of the EU.

Given the scale of the expected parliamentary defeat, however, these might not be enough. If Parliament does indeed vote down the proposed Brexit arrangements, where do we go next?

As with the earlier non-vote, this would probably depend on the scale of the defeat. A narrow margin might persuade the executive to try and vote again on the deal (perhaps with minor amendments), although the timing would be extremely tight. Another alternative would be to extend the Article 50 period, in which case Parliament might vote to also move the 21st Jan deadline to a later date. This would need unanimous agreement of other EU members.

Write for us. We're always on the lookout for talented writers and welcome submissions. Please send your opinion piece or pitch to: editor@commentcentral.co.uk

It would also beg the question of what would such an extension be for? After all, the EU is highly unlikely to negotiate something substantially different. A more substantive renegotiation would surely only be possible if it had an obvious conclusion amenable to the EU. We then face the fundamental question: what can realistically be changed that would be acceptable to the EU?

In order to avoid a hard border in Ireland, the north and south need to share a common customs territory and certain elements of the Single Market. One option is to alter the backstop such that the proposed customs union only encompassed Northern Ireland and not Great Britain. The problem with this is that Northern Ireland and Great Britain would then be in separate customs territories, which would enrage the Democratic Unionist Party and many Tory MPs still further. This was the initial EU proposal.

A fundamental challenge for the UK with regard to the Withdrawal Agreement lies in the deadline for extending it. The Agreement is structured so that the "sword of Damocles" represented by a 'no-deal' scenario will once again hang over the UK in the run-up to the point at which an extension to the transition period needs to be agreed. As such, the UK will be under pressure to make concessions to the EU in order to avoid disruption. It is unsurprising that MPs don't relish being put in this position come 2020.

Another option that has been posited as a "plan B" is the adoption of a "Norway-style" agreement as the future relationship. This would necessitate freedom of movement of labour, which is a red line for the UK Government. It raises problems for the EU, especially around Article 127 of the EEA (European Economic Area) agreement, which allows members to withdraw with one year's notice. As such, there would still be a need for a Withdrawal Agreement and a backstop, in case the UK later decided to withdraw from the EEA .

Such an arrangement would also almost certainly require more time than a modest extension of Article 50 would allow. At present, to become a member of the EEA, the UK would first need to (re)join EFTA (the European Free Trade Association). Naturally, other EFTA members would need to acquiesce to the UK joining EFTA and we know that there are concerns about this. The EU would be concerned about fishing rights, which is not covered under the EEA. The UK (or at least Northern Ireland) would still need to be in a common customs territory with the EU with all the disadvantages/problems that this entails .

If the appropriate executive action is taken, Parliament could vote for the UK to rescind Article 50 unilaterally. This would be something of a nuclear option. What they cannot do is, as some have suggested, suspend Article 50 by "temporarily" revoking it. The Court of Justice of the EU's ruling on the matter makes this very clear: revocation must be unequivocal and unconditional. It is thus difficult to imagine Parliament voting to revoke Article 50 without putting it to the country first leading to talk of another referendum .

This raises a number of tricky issues. There is now almost certainly insufficient time to properly organise a referendum prior to the 29th March. The meaningful vote will now not occur before 14th January. However, the EU might well be reticent about granting a longer extension to Article 50 due to the fact that there are elections to the European Parliament in late May 2019. In other words, the UK might well end up with insufficient time to hold a referendum .

Finally, a recent poll has highlighted that preferences between alternative Brexit scenarios remain on a knife-edge. The preferences of the populace at large are not clear and the results of any referendum would depend heavily on the nature of polling (three-way poll or a head-to-head) as well as which "marginal voters" decide to turn out. Fundamentally, whatever the outcome, a substantial portion of the population could feel disenfranchised .