I Am Invincible filly Supreme Idea has caused a massive upset at Randwick on Saturday, beating home short-priced favourite Dame Giselle to claim the Listed Lohnro Plate (1000m).

The two-year-old entered the race as a handy $14.00 shot with Ladbrokes.com.au but proved too good leading from start to finish. Jockey Tommy Berry enjoyed a gun ride in the saddle from barrier 10, before finding something extra over the final furlong to race away from challenging second place-getter Mission River.

Supreme Idea finished seventh in the Group 3 Blue Diamond Fillies Preview last month after winning on debut at Geelong on Boxing Day. After showing an enormous turn of foot on Saturday, the Anthony-Freedman hopeful has now firmed into $34.00 ahead of next months Group 1 Golden Slipper (1200m) on March 21.

While Supreme Idea caught punters by surprise, there were no excuses for $1.65 favourite Dame Giselle in third. The favourite struggled to make up ground down the straight and has now drifted from $12.00 out to $17.00 for the Slipper.

More to come.