Principally as very few have contested the event since it was established in 1861, only eight fillies have triumphed in the Derby at Randwick.

The latest of these is Shamrocker, a performer who suggested she could be a Cups heroine in the spring when she romped to an easy victory on Saturday in the 150th edition of the race, one now conducted under the banner of David Jones Australian Derby.

It was an effort that confirmed that Shamrocker, the only filly in the 14-runner field, is in the same class as most of the other seven of her sex who have won this historic classic.

Prepared at Flemington by Danny O’Brien for eight owners and now earner of over $1.8million, she has raced 12 times for four wins, including the Derby and two majors at Flemington, the Sires’ Produce Stakes and Australian Guineas. In addition she has been second in the Victoria Oaks and third in the Rosehill Guineas.

Shamrocker is the first filly to win the Derby since the Imperial Prince product Research was successful in1989. Research also won the AJC Oaks, Flight Stakes, VRC Oaks, Wakeful Stakes and STC Storm Queen Stakes and was runner up in the Caulfield Thousand Guineas, AJC Hobartville Stakes and STC Tea Rose Stakes.

In the decade in which Research was the winner, three fillies were successful in the Derby, the other two being Tristarc (1985; by Sir Tristram; five Group 1 wins, the AJC Derby, Queen Elizabeth Stakes, MRC Caulfield Cup, Underwood Stakes, Caulfield Stakes) and Rose of Kingston (1983, by Claude; won AJC Derby, Champagne Stakes, VRC Oaks, Ascot Vale Stakes, Craiglee Stakes, SAJC Australasian Oaks). Research and Rose of Kingston were each named Horse of the Year.

When Rose of Kingston won the Derby, she became the first filly to take the classic since Queensland bred Tea Rose (by Beau Pere’s half-brother Standfast) was victorious in1944.

She was also successful in the AJC Craven Plate, Rosehill Guineas and Canterbury Stakes and second in the AJC Oaks, Champagne Stakes and Sires’ Produce Stakes.

Tea Rose was the first female winner of the AJC Derby for the century, but there had been four in the 1800s, Clover (1865), Florence (1870), Nellie (1879) and Picture (1898). Florence challenges as the greatest performer among the eight Derby winning fillies, having the rare distinction winning three Derbys, AJC, VRC and QTC  – only two starters. She also won the Victoria Oaks and finished in third in the AJC Oaks.

Out of the seven AJC Derby winning females that preceded Shamrocker, Tristarc was the only one who went on to contest the Melbourne Cup, finishing eighth at four in1985.

Sharing the distinction with Tristarc of being one of only two New Zealand bred fillies to win the Derby, Shamrocker could get closer in the Cup if given the opportunity, particularly going on her maternal breeding.

On the sire side, she is by O’Reilly, a son of Last Tycoon got in Australia, foaled in New Zealand and a high class performer to1600m. He ran only six times, but wòn four races, including two Group1s.

Launched at the Waikato Stud near Matamata on a fee of $7,700 in1997, he is now one of Australasia’s best sires, supplying to date 440 winners of 1400 races and $62.8million.

His 47 stakes winners have included nine successful in Group1 events. One of them, Master O’Reilly, has been fourth in two Melbourne Cups.

Shamrocker’s dam was a sprinter but she was by Blues Traveller, a Bluebird English Derby third, and from Winter’s Tale, a daughter of Icelandic, sire of Desert Chill, winner of the Brisbane Cup (3200m) twice.

The bottom line goes back to a three-quarter sister-in-blood to Somerset Fair, a winner of 24 races, all stakes, to 2400m in 35 outings New Zealand and Australia.

Picture: Sportpix