Northern Ireland was given special status as a result of the 2019 Brexit "divorce" settlement between the UK and the EU.

While England, Scotland and Wales no longer follow EU rules, Northern Ireland still does, because it shares a land border with the Republic of Ireland, an EU member.

In order to avoid a physical border between the two countries - and thereby protect the peace process - it was agreed that customs checks would take place on goods entering Northern Ireland from elsewhere in the UK.