Chris Waller was the man who nudged Jim Cassidy over the line for his hallmark 100 Group One wins, and the two were in winning form again at Randwick.

The partnership between Cassidy and the hugely successful trainer bore the fruits of Cassidy's 98th, 99th and 100th Group One victories.

He won the Queensland Derby in June on Hawkspur, before jumping on super colt Zoustar to take out both September's Golden Rose at Rosehill and last Saturday's Coolmore Stud Stakes at Flemington.

On Saturday, the 50-year-old climbed aboard Waller's talented yet difficult Field Marshall in a benchmark 85 race and showed why he is nicknamed `The Pumper' when he got the gelding home in a four-way photo finish.

The four-year-old sat back and took his time picking up the pace, only to jolt forward in the final strides to pip Shamus by a nose.

Words Are Weapons was only a nose further behind, while California Storm was nearly as close in fourth.

"He's a little bit tricky to ride," Cassidy said of Field Marshall after the race.

"And I thought that if he was going to win he was only going to win in the last bit - 1100 (metres) he probably wins easy."

Cassidy said the horse "has a few tricks to him", but paid tribute to Waller for working out his personality.

"Even early he sort of wanted to run wide, and so I just sort of went with him and didn't really want to fight him.

"And providing he relaxed and didn't want to be aggressive he was going to finish hard.

Cassidy, whose milestone of wins was honoured by the Australian Turf Club in a trackside presentation at Randwick, had six rides on Saturday, with his next best result a second place on the Waller-trained Amovatio.