A legal challenge questioning what actions government needs to take before it triggers Article 50 is due to go to court next week.
The claimants are arguing that government does not have the power to trigger Article 50, and begin the UK's process of leaving the EU, by prerogative and that it can only be done after parliament passes an appropriate statute.
In particular, those bringing the challenge note the referendum was advisory, not binding, in nature and the European Referendum Act 2015 does not specify what the next steps following a Leave decision would be.
Although the government argues that the 2015 Act was passed on the understanding the outcome would be respected as a matter of policy, the claimants assert an understanding alone is not enough to create prerogative powers.
The courtroom is likely to be full to the brim during the three-day hearing, starting on 13 October and continuing on 17 and 18 October, as the case has been brought by a numerous parties.
However, the lead claimant is fund boss Gina Miller, who is being represented by solicitors Mishcon de Reya and counsel Lord Pannick QC and Tom Hickman of Blackstone Chambers, Rhodri Thompson QC of Matrix Chambers and Anneli Howard of Monckton Chambers.
The other named claimant in the case is Deir Tozetti Dos Santos, who is represented by solicitors Edwin Coe and counsel Dominic Chambers QC and Benjamin John of Maitland Chambers and Jessica Simor QC of Matrix Chambers.
Meanwhile, government recently revealed that Attorney General Jeremy Wright QC will be among its lawyers on case.
Wright said: "The country voted to leave the European Union, in a referendum approved by Act of Parliament. There must be no attempts to remain inside the EU, no attempts to re-join it through the back door, and no second referendum. We do not believe this case has legal merit."
At an earlier hearing in July to manage the proceedings, Sir Brian Leveson assured the claimants the case, along with any possible appeals stemming from it, would be heard before Article 50 was triggered.
At that hearing, lawyers for the government confirmed it was government's intention not to trigger Article 50 before the end of this year, and Prime Minister Theresa May has since said the official process for exiting the EU will be started before the end of March 2017.