Unraced as a two-year-old, the daughter of Danehill has thrived on her busy schedule this summer and was scoring for the fifth time from 10 starts as she cantered home under hands and heels riding from Johnny Murtagh.
Murtagh, very much the jockey of the moment, was content to see Trick Or Treat bowl along at the head of affairs and brought his mount down the outside of the pack to take control two furlongs out.
The 4-9 favourite then effortlessly strode further and further clear and was just nudged through the closing stages to account for Goodwood Cup winner Allegretto by four lengths, with Trick Or Treat five lengths back in third.
O’Brien, following several reverses over the first two days of the meeting, including Dylan Thomas’ runner-up finish in the Juddmonte International, said: “It was hard to get out of that second spot! She loves that ground and she is some machine.
“She loves racing and she prefers to race.
“Johnny came in and he said everyone knows that Dylan Thomas hates the ground he had yesterday and he really struggled for the first three furlongs, which is why Johnny came across to the rail to get the better ground.
“Johnny said she would have bolted in if she had run yesterday (in the International), but hindsight is a great thing.
“She was hacking there and she looks very good. She is very exciting and is open to everything.
“The Arc is very possible and she is getting better and better.”
It took Peeping Fawn four tries to break her maiden tag, after which she made rapid improvement and went on to be placed in the Irish 1000 Guineas and the Vodafone Oaks before embarking on her winning spree.
O’Brien continued: “You never know with any horse until you get them racing and get them into a rhythm, but some just start taking off and she is a typical example.