London mayor Boris Johnson has confirmed proposals for a ban on cyclists using a spectacular new bridge over the Thames.The £159m Garden Bridge is the brainchild of actress Joanna Lumley and has been designed by London 2012 cauldron creator Thomas Heatherwick.

A "Mayoral Decision" released online by City Hall on Friday night reveals the annual cost of "gardening" the garden bridge will be £2.5m.The bill, includes hiring a team of landscape gardeners and supervisors.The mayoral decision orders Transport for London to contribute £30m to the cost of building the bridge which will link Temple with the South Bank.

Artist's impression of the bridge Credit: Garden Bridge Trust

The government has also agreed to provide £30m. A charitable trust has been set up to raise the £99m balance from wealthy benefactors, donations and sponsors.The offer of public funding is conditional on the trust proving it can raise enough money to maintain the bridge for a "sustained period of time".The mayoral decision adds: "The Garden Bridge is designed for pedestrians and it is not possible to integrate facilities for cycling in the design given the number of pedestrians expected to use the bridge and it's function as a garden."