“I don’t believe it,” said Romeo. “It was one of the toughest days of my life so far.
“The breakaway, it was so hard to get into it, and I wasn’t feeling really good, so I waited to the last moment.
“I know in this kind of flat finish in a small break, I have good instinct, and that if they give me some seconds I can make it.
“I had this stage on my mind for a month. We’ve been doing altitude [training] at Sierra Nevada, working super hard with all the team, and they gave me this chance at the beginning of the week.”
Romeo was the under-23 time trial champion at last year’s World Championships and Tuesday’s success means he has a 17-second lead in the Dauphine’s general classification standings heading into the time trial.
Reigning Tour de France and Giro d’Italia champion Tadej Pogacar is just over a minute back in ninth and will aim to close the gap as the eight-stage race heads into the mountains on Friday.