It is prohibited to register a domain name directly under .uk (such as .internet.uk) and a second-level domain must be used (such as internet.co.uk). However, some domains delegated before the creation of Nominet UK remain.
- .bl.uk and .british-library.uk - British Library
- .icnet.uk - Imperial Cancer Research Fund
- .jet.uk - Joint European Torus
- .nel.uk - National Engineering Laboratory
- .nls.uk and .national-library-scotland.uk - National Library of Scotland
- .parliament.uk - Parliament of the United Kingdom