LAST week I was part of a cross party group who brought a case to the Court of Justice of the European Union to establish the conditions under which the UK’s Article 50 notice might be revoked.

We expect the case to establish as a matter of legal certainty that Brexit may be stopped by the UK revoking the Article 50 notice. 

The fact that the UK Government has fought this case tooth and nail at considerable expense shows how desperate the PM is to prevent MPs having this certainty.

READ MORE: ECJ Advocate General says UK can revoke Article 50 unilaterally 

The question matters because when MPs vote on whether to ratify the Withdrawal Agreement, a vote against ratification could result in a no-deal exit unless there is an alternative.

When he referred the case to Luxembourg, Scotland’s top judge said: “The answer will have the effect of clarifying the options open to MPs…..Whatever the interest of MSPs and MEPs, MPs have an interest in seeing the matter resolved.

"On that basis the petition is competent at least at the instance of an MP.”

The case was heard by the Grand Chamber of the Court comprising 26 judges.

Extraordinarily counsel for the UK Government refused to take a position on whether revocation is possible and argued only that the case was inadmissible.

READ MORE: Scotland's Brexit legal bid explained as European court to hear Article 50 challenge 

Normally where a party’s primary position is that the court should not entertain the question, a fall-back position would be advanced.Instead the UK government invited the court not to open up a Pandora’s box. However, in an eloquent summing up, our counsel, Aidan O’Neill QC, reminded the court that Pandora’s box also contained hope.

The other parties included two English MPs, who have intervened in the case to support our position, the EU Council and Commission. No one argued that the Article 50 notice cannot be revoked.

Indeed the Commission’s counsel said if there is a real change of circumstances and an authentic wish to Remain that would be a valid basis for revocation.

The key question the Court will answer is the conditions under which the notice can be revoked. We expect a final decision before Christmas and now that it is likely the PM’s deal will be defeated on  December 11 the Court’s decision could be pivotal in shaping what Parliament should do next.