Westminster is alive with anticipation of an imminent breakthrough on Brexit as Theresa May prepares to meet Jean-Claude Juncker in Brussels on Wednesday evening.
All hopes rest on attorney general Geoffrey Cox, who is expected to present the EU with draft legal language that would allow him to change his legal advice that Britain could be trapped indefinitely in the Northern Ireland backstop.
Cox wants the EU to make explicit the temporary nature of the backstop on the grounds that article 50 cannot be the basis for Britain’s future relationship with the EU, only for its withdrawal.
The EU is willing to consider the proposal if it is presented, but two potential problems are apparent already.
One is that the backstop rests on two separate legal pillars. Its Northern Ireland-only measures are supported by the EU law underpinning the areas of North-South co-operation outlined in the Belfast Agreement. These can be open-ended.
The UK-wide customs arrangement, on the other hand, is based on article 50, and the EU accepts that it must be a starting point for the future relationship rather than a landing zone. EU negotiators are happy to consider fresh legal assurances that the UK-wide backstop measures – which the British government requested – must be temporary.
But they cannot offer the same assurances about the Northern Ireland-only elements which matter most to the DUP, whose support the prime minister views as essential to winning over a sufficient number of her own backbench Brexiteers.
Legal form
The second likely difficulty surrounds the legal form any fresh assurances should take. Downing Street continues to insist that May is seeking changes to the withdrawal agreement itself, something the EU has ruled out. Not one of the EU 27 leaders has yet called, publicly or privately, for the text of the agreement to be reopened.
Some at Westminster expect Cox to ask for a legally-binding codicil to the agreement but the EU does not use codicils. Brussels will not agree to a protocol which would be part of the withdrawal agreement and, consequently, would represent a change to it.
The most likely form is a joint interpretive instrument, similar to that signed alongside the EU's trade deal with Canada, a document with legal force clarifying the meaning of parts of the agreement as understood by both parties.
If Cox fails to win assurances about the temporary nature of the Northern Ireland-only measures in the backstop and the guarantees he does secure are separate from the withdrawal agreement itself, it may feel like something less than a breakthrough at Westminster.