The papers are reporting that Best For Britain has mounted a legal challenge to force the Government to concede that a second EU referendum is legally necessary.
The claim is based on the argument that the 2011 European Union Act guarantees a new referendum if the Government seeks to remain part of EU bodies such as the European Medicines Agency.
The Government counter-arguments is that the EU Withdrawal Bill revokes the 2011 European Union Act.
The Best For Britain argument is that the EU Withdrawal Bill is just that, a Bill - and not law and that the UK is negotiating with the EU under existing British law - hence the trigger for a second referendum.
It sounds weak, but who knows - maybe it will be the hole in the dam that upsets things.
Who is Best For Britain
I see that the CEO of Best For Britain (Eloise Todd) writes for the Guardian. I don't know anything about the Board members. The registrar is Giles Norris and there is a DDG search that refers to an article he wrote on their site - but it doesn't link.