One of the most unusual discoveries from the Thames in recent years, a ball and chain dating from the 17th - 18th century, goes on display at Museum of London Docklands today.

Museum experts believe it would have been used to shackle prisoners during transport, but it was uncovered with the lock fastened and no key. This raises the possibility that a prisoner may have slipped out of custody, although a less happy outcome would probably have awaited the unfortunate person who found themselves fettered in the river.

The find was uncovered by Steve Brooker and Rick Jones, mudlarks who thought they were looking at a cannon ball until the attached chain slithered out of the Thameside mud. The foreshore has large areas of thick black mud which preserves objects that would in other conditions corrode or rot away. The ball and chain is made from iron and weighs 8kg. The padlock has a brass plate around the key hole, and is skilfully crafted in a continental fashion...