Heather Watson into 2017 Australian Open second round after beating Samantha Stosur

The 24-year-old Brit joined compatriot Johanna Konta in the second round after a contest lasting two hours and 15 minutes against the 18th seed in Melbourne.

Watson was broken in the first game of the match and again early in the second set but, after several gruelling games, eventually surged clear in the decider.

Her reward for beating a player 60 places higher in the world rankings is a second-round tie against either American Jennifer Brady or Belgian Maryna Zanevska.

Stosur, whose defeat extends her disappointing record in her home grand slam, broke Watson in the opening game but the world number 81 swiftly fought back to reel off five straight games.

The Stosur forehand soon began to cave under pressure but it was a missed backhand which gave Watson a crucial second break at 4-2 as she took the opening set 6-3.

The second set also started badly for Watson, as former US Open champion Stosur broke when her opponent netted a routine forehand.

Down 3-1, Watson unsuccessfully challenged a backhand down the line at deuce as she tried to engineer a break back and wasted three break points in a marathon seventh game of the set before Stosur went 5-2 ahead with an ace as she went on to square the contest.

With the backing of the home crowd, Stosur might have expected to carry that momentum into the third set but failed to take advantage of a break point in the first game and found herself 2-0 when Watson produced a sensational forehand down the line at 15-40.

Stosur led 30-0 in the fourth game but suffered another sudden loss of confidence and some tentative play eventually gave Watson a 4-0 lead, with the Brit racing through the next two games to progress.

"I'm very pleased with today," Watson said on court afterwards. "Sam's a great player, I've played her a couple of times before and she's beaten me both times.

"I played really well today. T here were some very long games; I had a slow start in both the first two sets so I wanted to get off to a good start in the third and make her work for everything, and I think I did."