British number one Dan Evans came back from two sets down for the first time to beat American Mackenzie McDonald and reach the Australian Open second round.
Evans, playing his first Grand Slam as a seed, looked edgy in the first two sets on a packed outside court, showing his frustration at times.
But the 30th seed settled down to win 3-6 4-6 6-1 6-2 6-3 in Melbourne.
Fellow Britons Johanna Konta and Kyle Edmund play later on the opening day of the first Grand Slam of the year.
Evans' victory sets up a second-round match against Japan's Yoshihito Nishioka.
If the 29-year-old wins that then he could face 16-time Grand Slam winner and defending champion Novak Djokovic in the third round.
Evans ends run at 15th attempt
Evans had never won a five-set match after losing the opening two, finally ending that run at the 15th attempt against a tiring McDonald.
A pinpoint forehand winner down the line, on his first match point, sealed the Briton's place in the second round following a battle lasting three hours and 21 minutes.
Evans has the luxury of avoiding the big names in the early rounds of the men's draw after climbing to a career-high 32nd in the latest ATP rankings released on Monday.
But he was made to work hard by 129th-ranked McKenzie, a talented player who has slipped down the rankings after an injury-hit 2018.
Evans was tight in the opening two sets and was seemingly distracted by fans standing in the aisles because they could not find an empty seat.
"I was frustrated. I wasn't playing my game, hitting the ball in," Evans said.
"I was impatient at the start and trying to come in too early."
After lacking patience and precision as he seemingly stared at defeat, Evans suddenly found the form which has propelled him up the rankings over the past 18 months.
A more positive approach started to pay off as McDonald, playing only his second tournament since last May after having surgery on a hamstring tendon, started to struggle.
Evans twice broke the American's serve early on in the third and fourth sets and, after needing to dig deep again in a fifth set where the players exchanged six breaks, came through.
"I just hung in, I thought my level was there somewhere," the Briton said.
"I changed my game a little bit, started making few more balls and in the end I was pretty strong."
Evans pointed to his stomach on his way to shaking hands with McDonald, a gesture seemingly directed at Britain's former world number four Tim Henman.
After bonding with Evans in his role as British captain at the ATP Cup, Henman jokingly suggesting at the end of the tournament Evans needed to "miss a few meals" if he wanted to break into the world's top 20.
"It was just a joke, there was nothing in it," Evans laughed when asked about his gesture.