Kew Gardens Trustees have announced that the London Eye architects are to build a spiral walkway to take visitors 60ft aloft into the tree canopy of the Royal Botanic Gardens.

The 656ft walkway (costing £3m) will snake through the treetops of chestnuts planted by Lancelot "Capability" Brown, the landscape gardener, in the 18th century.

Kew is adopting techniques used by the Eden Project in Cornwall, which combines a theme park experience with botanical lessons.

Construction starts in June and the walkway is expected to open in May 2008.

This innovation should help Kew’s campaign to boost visitor numbers up and away from the current level of 1.9 million a year.