The principle of mutual trust is central to EU law. According to the CJEU, this principle is not applicable in relations between the EU and non-Member States. In these circumstances, trust is judicialised through lesser mutual recognition agreements, equivalence mechanisms, non-regression clauses or, in the current case of the UK, proposed level playing field commitments. The EU-UK relationship is unique in involving a former Member State. Below any political agreement, the role of regulators will be significant in managing the extent of regulatory equivalence. The uneasy balance between cooperation and competition raises the question of trust between regulators, shifting beyond the legalised system of mutual trust within the EU. In addition to analysing proposals for governance mechanisms, this paper draws upon political science and social theory literature in assessing the conditions and prospects for regulatory trust in the future relationship between the EU and UK.