Vow overcame greenness to run out an ultimately impressive winner of the Betfred "The Bonus King" Oaks Trial at Lingfield on Saturday.
William Haggas' charge had won a Newbury maiden on her debut last month and and was travelling strongly alongside leader Estrela turning for home.
The daughter of Motivator picked up well but just as he looked set to surge clear, she hung towards the stands' rail.
Johnny Murtagh never resorted to the whip and the 11-10 favourite was soon back on an even keel, going on to score by three-and-a-quarter lengths from Colima (5-1). Estrela (11-2) was a further five lengths away in third.
Sky Bet halved the winner in price to 8-1 for the Investec Oaks. Betfred are teh same price, Coral as low as 5-1 but Ladbrokes are a stand-out 14-1.
Vow runs in the silks of Highclere Thoroughbred Racing Pocahontas syndicate, whose MD Harry Herbert said: "Johnny said she was very green when she came into the straight.
"She ducked away towards the stands but it didn't stop her, she's got a proper engine. She has such a fabulous action, and as she's by Motivator whose progeny tend to handle cut we wouldn't be too worried if it was soft at Epsom, but ideally we want better ground.
"Both William and Maureen (Haggas) are definite in their belief that she would prefer that. It's fantastic for the owners who at this moment have the second-favourite for the Derby (Bonfire) and a live contender for the Oaks.
"When Maureen chose her to ride in her work we thought it might be a good omen as she did the same with Dancing Rain last year.
"We will need to talk to William and Maureen, but I imagine it will be the Oaks as long as she's OK."