How many years between the last hill forts and the surge of motte and Bailey castles?

The last hill forts in Britain were largely abandoned by around the 1st century AD, while the surge of motte and bailey castles began in the late 11th century, following the Norman Conquest of 1066. This indicates a gap of approximately 1,000 years between the decline of hill forts and the rise of motte and bailey castles.