Chinese artist Ai Weiwei unveils giant London work

Covering 1,000 square meters at the east end of the converted power station, the installment called "Sunflower Seeds" is 10 centimeters deep and weighs a total of 150 tonnes.

The seeds appear at first to be identical, but are in fact painstakingly crafted and painted using traditional methods by 1,600 skilled artisans from the Chinese city of Jingdezhen.

Ai, 53, said the work was designed to reflect the concepts of individualism, mass production and craftsmanship. He also traced a connection to his use of social networking platform Twitter, which he saw as a tool to reach out to China's youth.

Unusually for a work of art in a gallery, visitors are allowed to walk over the seeds, and video screens have been set up to allow them to record video questions which are sent to the artist to respond to online.