How is tamworth castle a motte and bailey?

Tamworth Castle is not a motte and bailey castle, it is a ringwork castle. A motte and bailey castle is a medieval fortification consisting of a large mound of earth or stone (the motte) topped with a wooden or stone tower, and a bailey, a defended enclosure surrounding the motte. There are over 600 known examples of motte-and-bailey castles in England, and they were most common in the 11th and 12th centuries. Tamworth Castle, on the other hand, was built in the 11th century as a ringwork castle, a type of castle with a circular or oval enclosure surrounded by a ditch and palisade.