Plymouth is a port city and unitary authority in Devon, South West England. It is located on Devon's south coast between the rivers Plym and Tamar, about 36 miles southwest of Exeter and 193 miles southwest of London. It is the most populous city in Devon. Plymouth's history extends back to the Bronze Age, evolving from a trading post at Mount Batten into the thriving market town of Sutton, which was formally re-named as Plymouth in 1439 when it was made a borough.