Melbourne mare Secret Agenda has overcome a wide draw to win Adelaide's first $1 million race at Morphettville.

Saturday's Group One UBET Classic (1200m) had a prize money injection this year, which attracted a top-class field of fillies and mares from around Australia.

Secret Agenda, ridden by Damien Oliver, showed blistering early speed to come across from barrier 16 in the 20-horse line-up to lead by the 800m mark.

Rated perfectly in front by Oliver, Secret Agenda ($15) kicked clear soon after straightening, holding off fast-finishing local mare Viddora ($8.50) by 1-3/4 lengths, with another Victorian-trained filly, I Am A Star ($6), close up in third place.

The victory by Secret Agenda was her first at Group One level and came on top of her win during The Championships, when she won the Sapphire Stakes at Randwick.

It was Oliver's second win in the Group One race after success on Alinghi in 2005, while trainer Mick Price had tasted previous success in the race with Bel Mer in 2009.