Wallasea Island: The nature reserve built with CrossRail's leftovers

Ten years ago the RSPB took over Wallasea Island in Essex, with the intention of making it a welcoming space for 50,000 visiting birds.

Left alone, the island would have been lost to the sea, a casualty of climate change and coastal erosion.

Saving and restoring Wallasea was made possible because of Europe's biggest engineering project London Crossrail. Millions of tonnes of earth excavated from beneath the capital had to be disposed of, and the RSPB had just the place.

It used the earth to bring part of the island to a metre and half above sea level, and then moulded it to create a new shape to the island, with new sea walls and a mosaic of mudflats and lagoons.

Once this was done, the sea walls were breached and the high tide came in.

This time-lapse RSPB footage shows how water has been controlled to give wildlife a home.