Cornwall and west Devon were once the biggest tin and copper producers

The go-ahead by Unesco, the United Nations' cultural organisation, would give the area the same status as the Great Wall of China and the Taj Mahal.

The team behind the bid wants to preserve 10 mining areas from St Just in the west to the Tamar valley

In the 18th and 19th Centuries the mines of the area were the world's largest source of tin and copper.

The World Heritage Convention, adopted by Unesco in 1972, provides for the identification, protection and conservation of natural and cultural sites of outstanding universal value.

World class

More than 800 such sites can be found across the world, including 628 cultural, 160 natural and 24 mixed properties in 137 countries.

Cultural examples on the list also include the Tower of London.

The Cornwall and west Devon world heritage site bid was submitted for nomination by the government in January 2005.

A period of extensive assessment by Unesco's advisers has followed with the announcement expected from Unesco on Thursday evening.

World Heritage status would give recognition to the area's excellence as a world class cultural and heritage site.

It also recognises the importance of the historic landscapes and outstanding buildings in addition to its important role in technological innovation and scientific research.