Make Your Own Xmas, 2008, © Bob and Roberta Smith, Photo: Sam Drake, Tate Photography

This year's Tate Christmas Tree, which is designed each year by a different artist, is by Bob and Roberta Smith and aptly reflects the ecologically minded times that we now live in. The tree is made from timber, bicycles and lamps, and is interactive, with visitors asked to provide pedal-power to illuminate the tree.

Tate visitors provide pedal power to light the tree (loving the guy on the left's expression)

Standing at 11 metres in height, the tree itself is constructed from recycled materials, including sandwich boards and a oil drum. Eight bikes are then fixed to stands around the trunk, each holding a generator that is connected to a set of light bulbs that decorate the tree.

The tree will be on display at Tate Britain until January 4.