State hostage-taking, where individuals are arbitrarily detained by foreign governments for diplomatic leverage, involves serious violations of human rights, including the right not to be subjected to torture and ill-treatment. It is widely accepted that the practice of State hostage-taking is increasing internationally. British nationals are among the most frequent targets of hostage-taking globally, and face some of the worse outcomes. This briefing outlines why the UK government should introduce a Special Envoy for Complex and Arbitrary Detentions with sufficient authority, resource, and mandate to lead diplomatic responses, while treating families as trusted partners.