The details of the deal were published in a government paper titled 'Safeguarding the Union" before a statement in parliament.

The executive summary of the paper said the measures in it were designed to "guarantee the smooth flow of Great Britain to Northern Ireland trade" and "guarantee unfettered access for Northern Ireland goods to the rest of the UK on a permanent basis".

"This paper sets out a range of measures that, in the event of the restoration and ongoing functioning of the institutions, would copper-fasten Northern Ireland's political and constitutional place in the Union, strengthen the operation of the UK internal market, and support ever greater opportunities for trade within it - responding to the deeply held concerns that have been expressed."

(Reporting by Sarah Young and Elizabeth Piper, writing by William James; Editing by Kate Holton)