Oddly, the idea for the design came from Absolutely Fabulous actress Joanna Lumley, who approached Heatherwick years ago. The bridge would be a new structure across the river intended to help improve pedestrian life by connecting North and South London with a planted garden path landscaped by U.K. designer and horticulturalist Dan Pearson. It would be filled with indigenous river edge trees, shrubs, and wildflowers and include benches and walkways of varying widths to create both intimate and more expansive spaces along the walkway. If built, the bridge would be an obvious crowdpleaser as a public green space, lookout point, and tourist destination. In London it would be a rare new jewel in the crown of a city already famed for its gardens.
Source : http://www.slate.com/blogs/the_eye/2013/12/05/the_garden_bridge_london_s_answer_to_the_high_line.html