Complex sentence: This was later joined to what is now the church of St-Jean-Baptiste and the tower was only converted to a belfry after the sea retired, leaving it 1.5 kilometres inland.
Split into simpler sentences: This was later extended to join the tower, making what is now the church of St-Jean-Baptiste. The tower was only converted to a belfry after the sea retired, leaving it 1.5 kilometres inland.