Complex sentence: On the restoration of Charles II, his Viceroy in Dublin, Lord Ormonde established a Royal Hunting Park in 1662 which contained pheasants and wild deer, therefore it was necessary to enclose the entire area with a wall.
Split into simpler sentences: On the restoration of Charles II of England, his Viceroy in Dublin, the Duke of Ormonde, established a Royal Hunting Park on the land in 1662. It contained pheasants and wild deer, making it was necessary to enclose the entire area with a wall.