Dyer, who takes a team of horses to the Northern Territory each year, won the 2050m feature race with seven-year-old Royal Request ($8).

He and winning jockey Jarrod Todd immediately dedicated the win to jockey Roger Booth, who died after suffering a cardiac arrest at a Darwin Turf Club meeting on July 1.

The 55-year-old collapsed in the mounting yard after partnering the Dyer-trained Senor Juez into sixth position in a 1200m event.

A medical team was able to revive Booth and he was conscious while being transported to Darwin Hospital, but he later suffered a heart attack and died.

"Roger was a great mate of mine," Todd told Sky Thoroughbred Central.

"He was on my back for that one."

Royal Request, a Northern Territory Derby winner in 2014, was having his fourth start in the cup.

He was unplaced in 2014, before finishing second in 2015 and fourth in last years race.

The gelding had won six of 14 starts in Darwin before Mondays race, including back-to-back wins over 1600m during July.

The win required a massive effort, with the sole Victorian horse in the race carrying the top weight of 61.5kg, but he was able to overhaul Saturday Sorcerer in the straight and win by three-lengths.

"It's been a rough old time and Jarrod and I were both thinking of him (Booth) today," Dyer said.

"I thought he (Royal Request) was the best horse in the race but I was worried about the weight."

Dyer previously won consecutive cups in 2011-12 with Hawks Bay.

He took 20 horses to the Northern Territory for this years carnival.

Royal Request, whose first race win came at Darwin in start number three in August 2013, has now won 12 of 51 career starts, for total prize money of $551,944.