Bookmakers betting on the Melbourne Cup are not the only ones impressed by the Irish St Leger win of Wicklow Brave.

Greg Carpenter, head of handicapping at Racing Victoria, announced on Tuesday he had allocated the Willie Mullins-trained stayer 55kg for November's Melbourne Cup at Flemington after his win over odds-on favourite Order Of St George at The Curragh on Sunday.

The weight is 2.5kg more than Carpenter handed the stayer in the Caulfield Cup when he released weights for that race two weeks ago.

Leigh Jordon, RV's recruitment officer, said Mullins had already placed Wicklow Brave in quarantine for a trip to Melbourne.

Before his Irish St Leger success Wicklow Brave was at $81 in Cup betting but had his price slashed to $15 favouritism after his weight was announced.

Wicklow Brave will be the fourth horse Mullins has sent to Melbourne for the Cup.

Holy Orders finish 17th in 2003, Simenon fourth in 2013 and Max Dynamite second to Prince Of Penzance last year.

"Wicklow Brave is locked away," Jordon said.

"He'll be out here early like Max Dynamite was last year. That's the way Willie likes to do things."

Order Of St George and 2014 Cup winner Protectionist share equal topweight of 58kg for the $6.2 million race.

But the pair face a 66-year hoodoo to win the race.

The last original Cup topweight to win was Comic Court in 1950 with 59.5kg.

"The handicap presents a challenge to both Order Of St George and Protectionist, however they have earned the position at the head of the weights based on their performances over the past 12 months," Carpenter said.

Last year's winner Prince Of Penzance rises 3.5kg on 2015 to 56.5kg.

The 3.5kg rise is the same given to Americain (2011) and Dunaden (2012) following their respective Cup victories.

Victoria Derby winner Tarzino and Australian Derby winner Tavago are the highest rated four-year-olds with 54kg, with VRC Oaks winner Jameka guaranteed a start with 51.5kg.

Preferment, a four-time Group One winner, has won the most number of races at the highest level of the 123 horses nominated and with 56.5kg shares the second highest weight with Prince Of Penzance.

Should Order Of St George and Protectionist not run, weights will rise a minimum of 0.5kg to obtain a 57kg minimum topweight under Australian rules of racing.