Complex sentence: The 2004 Cook Cup was contested over two matches and the second game was played at Twickenham, with Australia winning by 21 points to 19, which saw the Wallabies win the Cook Cup.
Split into simpler sentences: The 2004 Cook Cup was contested over two matches. So the second game was played at Twickenham, and Australia won 21 to 19, which saw the Wallabies win the Cook Cup.