Complex sentence: The ship was chartered by Brittany Ferries from 17 April 1978 initially to sail on the Portsmouth-Santander her main route was Portsmouth-Saint Malo and was renamed MS "Prince of Brittany".
Split into simpler sentences: The ship was chartered by Brittany Ferries from 17 April 1978 initially to sail on the Portsmouth-Santander route. Her main route was Portsmouth-Saint Malo and she was renamed MS "Prince of Brittany".