The United Kingdom is not a federal State but has a significantly decentralized structure in respect of Scotland, Wales and Northern Ireland. While there was no question, then, that the national government had sufficient constitutional authority to unilaterally ratify and implement OPCAT, in practice a consultative process was undertaken in order to ensure effective support and implementation throughout the UK.
Prior to signing the OPCAT, the Human Rights department of the UK Foreign Office consulted with all national government departments likely to be affected, with independent statutory authorities, and with the devolved administrations in Scotland, Wales, and Northern Ireland. All the entities concerned confirmed to the national government that an existing body that met the requirements of OPCAT already covered them. The national government concluded that the NPMs required for OPCAT were already in place and no new mechanism needed to be created. All departments gave their consent to ratification and designation of NPMs under OPCAT. Thus, there was never a proposal to create new visiting mechanisms in the UK to comply with OPCAT. Article 3 of OPCAT explicitly recognizes that NPMs can be one or several.
Prior to ratification, the UK created a list of independent bodies potentially relevant to the OPCAT. Some were regional: in England and Wales, for instance, the list of mechanisms included various Inspectorates for prisons and youth detention centres, lay visits to police custody facilities, visits to court lock-ups and psychiatric hospitals. UK-wide there were immigration and asylum-seeker detention and removal centres. Maintaining links between the International Subcommittee and the multiplicity of UK NPMs was considered an administrative challenge. Originally the thinking was that the Subcommittee would work directly with all the UK NPMs. Then, the UK considered designating whether some of the larger bodies should be tasked with co-ordinating roles.
On 24 February 2014, the UK extended OPCAT ratification to the territory of the Isle of Man.