“relevant UK authority”

1. European Union (Withdrawal) Act 2018 Act
2. Extradition Act 2003 Act
3. Finance Act 2011 Act 2 definitions
4. Regulation (EC) No 1072/2009 of the European Parliament and of the Council of 21 October 2009 on common rules for access to the international road haulage market (recast) (Text with EEA relevance) EU regulation

Definitions are taken from the instruments as published on zoomLaw, for guidance only. Check the instrument itself for its scope and any amendments.