If Rostova wins the Golden Slipper, and King is confident she can, the 39-year-old will join an elite group of riders to claim Australian racing's grand slam.

Only six others Neville Sellwood, Roy Higgins, Pat Hyland, Mick Dittman, Jim Cassidy and Damien Oliver have won the Melbourne Cup, Caulfield Cup, Cox Plate and Golden Slipper.

King won the Caulfield-Melbourne Cup double on Let's Elope in 1991 and the 2003 Cox Plate on Fields of Omagh and would like nothing more than to complete the set.

''It's something every jockey wants to do and few have,'' King said. ''It is certainly something I have always wanted to do and Rostova is my best chance in the Slipper for sure.''

The only blot on Rostova's record was the Blue Diamond.

King and trainer Steve Richards believe she choked down after getting her tongue over the bit and a gear adjustment was made.

The filly came out at her next start wearing a tongue tie and duly won the Group2 VRC Sires' Produce Stakes.

Rostova was not among the original nominations for the Slipper but her Sires' Produce win convinced her owners to pay the $150,000 late entry fee. Since being confirmed as a starter, Rostova has been steady on the third line of betting with most agencies behind Real Saga and More Joyous.

''I was riding Littorio last spring and Rostova was next door to him at Flemington so I got to know her well,'' King said.

''She is a temperamental filly but I knew she was something very special early on.''

Rostova won her first three starts before faltering in the Blue Diamond and has maintained her condition and fitness.

''Her first wins were soft wins, all very soft,'' King said.

''The Blue Diamond she only went for half a mile [800m] and then she choked down so she really didn't have a hard run.''

In keeping with his policy of finding the right horse and sticking to it, King has given up rides in Melbourne over the past couple of weeks to help Rostova settle in to life in Sydney.

She ran second to Slipper rival Reward For Effort in a barrier trial last Friday and has adapted admirably to the right-handed way of racing.

''She needed the experience going the Sydney way and I was happy with how she handled it and how she has done since,'' King said.

''She seems focused.''

As is her jockey. AAP