Irish trainer Willie Mullins says he is surprised to hear Wicklow Brave is at the head of Melbourne Cup markets after his St Leger win in Ireland over one-time favourite Order Of St George.

Order Of St George was given equal topweight of 58kg with 2014 winner Protectionist when Melbourne Cup weights were announced on Tuesday.

But both have been taken out of markets amid reports they will not make the trip to Australia.

If neither come, Cup weights will need to be raised 0.5kg to have a minimum topweight of 57kg with last year's winner Prince Of Penzance and Preferment the next highest in the weights.

The Mullins-trained Wicklow Brave, who was given 55kg, was promoted to $15 favourite after winning the St Leger at The Curragh on Sunday.

"It surprised me, but there you are," Mullins told RSN927

"Form going into the race is worth an awful lot. You can have all the form from last year you want, but present form is worth so much."

Wicklow Brave has been joined at the top of TAB's Cup market by English horse Big Orange who was fifth in the race last year.

Wicklow Brave was given 52.5kg in the Caulfield Cup but his Irish St Leger win prompted Racing Victoria's chief handicapper Greg Carpenter to raise his weight by 2.5kg for the Melbourne Cup.

Mullins said the handicapper obviously wasn't under-rating the gelding by giving him that weight after he booked the trip to Australia.

"We won a beautiful race to get there. It pays for everything," Mullins said.

"And we still have a racing weight."

Mullins finished fourth in the Cup with Simenon in 2013 and second with Max Dynamite last year with the latter carrying 55kg.

"Both horses were improving at this time of the year," Mullins said comparing Wicklow Brave to Max Dynamite.

"So I just probably need a bit more improvement from our fellow."

He believes Wicklow Brave has improvement in him and the St Leger win was a nice surprise.

"We were hoping to be placed, but to get the win was probably a huge bonus."

Wicklow Brave is due to arrive in Melbourne with the first shipment of international carnival competitiors on October 1.