Complex sentence: The first, the church of Saint Margaret retains just the walls of its west tower and part of the west end of the nave, constructed in flint and limestone and thought to date to the 12th and 13th centuries.
Split into simpler sentences: The first, the church of Saint Margaret, retains just the walls of its west tower and part of the west end of the nave. It was constructed in flint and limestone, and is thought to date to the 12th and 13th centuries.