Of Waller's horses competing, Who Shot Thebarman - owned by brothers Michael, Dan, Humphrey and Shaun O'Leary - is the most fancied to win, with odds at $21 behind Junoob ($26) and Opinion ($51).
The brothers, who shot to fame in local racing circles after their horse won this year's Auckland Cup, said the name Who Shot Thebarman was inspired by their aunt's favourite quip at finding her gin glass empty.
Waller, quietly spoken and courteous to a fault, will likely burst into tears if the horse takes out the A$6.2 million ($6.96 million) Emirates Melbourne Cup.
The trainer - who began in Foxton - often cries unashamedly after major victories. Part of it appears to be a great admiration for the horses that have allowed him to put racing royalty like Gai Waterhouse and Lee Freedman in the shade since arriving in Australia a decade ago with a maxed out credit card and large dreams. Perhaps it's because he realises he possesses a great skill.
His record in the last three years is beyond head shaking.
At Flemington on Saturday he won the A$1.5 million Victoria Derby, the A$500,000 Coolmore Stakes and missed by a whisker to add the A$1 million Mackinnon Stakes.
You get the feeling Waller is hopeful more than confident Who Shot Thebarman can win the big race.
Glen Boss, who will be riding the horse, won three Melbourne Cups on the great Makybe Diva.
"I can see him [Who Shot Thebarman] running top 10, the rest will probably be down to luck," Boss said yesterday.
"I wouldn't be staggered if he won it, but I wouldn't be staggered if he finished fifth either."
In the lead-up to today's big race, Who Shot Thebarman has been building a profile in Australia.
On October 5, Boss took the horse away from the field in the group three 2520m race at Flemington, adding to his last-start win at Australia's racing headquarters over 2000m, winning by two-and-a-half lengths.
That victory was the eighth from 14 starts, earning a spot in the A$3 million Caulfield Cup (2400m).
Unfortunately, Boss and the horse finished 13th in the October 18 race, while Japan's Admire Rakti produced a powerful sprint to win the race from Kiwi mare Rising Romance, and race favourite Lucia Valentina finished third.
Today, Admire Rakti - the sole Japanese runner - is the $4.60 favourite.