Royal Marine Ciarán Maxwell from Larne, Co Antrim, has appeared in court in London charged with Northern Ireland-linked terror offences.
The 30-year-old, with an address in Exminster, Devon, is accused of stashing explosives and weapons in purpose-built caches in England and Northern Ireland.
He also allegedly compiled a library of terrorism documents, including instructions on how to make explosives and tactics used by terrorist organisations.
Maxwell appeared in custody at Westminster Magistrates' Court on Friday.
Wearing a grey tracksuit and flanked by two plain-clothed officers in the dock, he stood up to confirm his details.
He has not yet entered any plea to the charges against him and was remanded into police custody.
The case was adjourned until Monday at Westminster Magistrates’ Court to give the police more time to investigate.
It is alleged that between 1 January 2011 and 24 August 2016, Maxwell manufactured explosive substances and constructed explosive devices.
He is accused of carrying out research resulting in the creation of a library of documents likely to be useful to someone committing or preparing an act of terrorism - specifically information regarding "the manufacture of explosive substances, the construction of explosive devices and tactics used by terrorist organisations".
Maxwell is also charged with getting an image of an adapted PSNI pass card and items of PSNI uniform.
The Metropolitan Police said he is charged with "creating and maintaining hides in England and Northern Ireland to store explosive substances, explosive devices, components for explosive devices, ammunition, weapons, tools and resources used during the construction of explosive devices and assorted other items linked to the preparation of an act of terrorism".