Australian Prime Minister said the horse to watch in the Melbourne Cup is Shocking.

Speaking in Townsville, Rudd days he tips Shocking to win because it has done reasonably in various Queensland starts.

Meanwhile, a cool day with a top temperature of 20 degrees is forecast and the Victorian Racing Club is expecting a crowd of more than 100,000.

The eldest granddaughter of Queen Elizabeth II, 28 year old Zara Phillips will attend the event and present the winning jockey with the trophy.

Bart Cummings, with his horses the sentimental favourites, is seeking his 13th Melbourne Cup win, with last year's winner and favourite Viewed.

The South Australian gelding Alcopop is another favourite.

The Melbourne Cup will start at 4pm.