The opening race at Caulfield has been decided in the stewards' room with Ma Jones' rider Ben Allen successfully lodging a protest against the horse who was first past the post.

Quilate, ridden by Melbourne's leading apprentice Beau Mertens, was first across the line in Saturday's Jack Elliott Handicap but Allen fired in a protest alleging Mertens shifted out over the final 200m.

The margin was a short neck.

While acknowledging he did shift out, Mertens told stewards he felt Allen never stopped riding his mount and said that horse still had every chance to run him down.

Chief steward Terry Bailey ruled that if Ma Jones been afforded an unimpeded run without Mertens shifting out, she would have finished in front of that mare.

Mertens and Allen are Melbourne's two leading apprentices this season.

Allen started Saturday's meeting 10 wins behind Mertens in the metropolitan apprentices' premiership.