Sites can only be nominated for inclusion on the World Heritage List by a national government. Once nominated, they are rigorously evaluated by either ICOMOS (for cultural sites) or IUCN (for natural sites) or both (for mixed sites and cultural landscapes). ICOMOS and IUCN recommend to the World Heritage Committee whether or not a site should be inscribed on the World Heritage List.
Only the Committee can actually decide whether or not a site has Outstanding Universal Value and should be placed on the List. Success is by no means assured and over the years several UK nominations have failed or had to be revised and re-submitted.
Before any site can be nominated it must first be on the national Tentative List. This is a list of places which a State Party considers that it might nominate over future years. Tentative Lists have to be formally submitted to UNESCO and are expected to be reviewed about once every ten years.
Following a review of World Heritage policy including the 1999 Tentative List of the United Kindom and Northen Ireland, the UK government, taking advice from an Expert Panel, published a new Tentative List in 2011 which listed 13 sites for potential nomination. In 2014, a further site was added to the UK Tentative List - Great Spas of Europe, a transnational candidate site which includes the City of Bath. This revised UK Tentative List was submitted to UNESCO in 2014. The Expert Panel's report explains the rationale for the selection of sites on the Tentative List.
Once candidate sites have been placed on the UK Tentative List, they are invited to put forward a more detailed case for nomination. These submissions are then subject to 'technical evaluation' by and expert panel chaired by the UK National Commission for UNESCO. Only those places that have put forwrad a robust and convincing case to meet the testing criteria for selection oin the World Heritage List will be formally submitted to UNESCO by the Secretary of State for Culture, Media and Sport.
The next UK nomination to go forward to UNESCO will be the Lake District in 2016.