Katie Boulter is resilient in defence, but eventually the pressure tells and Rebecca Marino swats a forehand past the Briton.

But it's Boulter with the magic on the next point, lobbing the Canadian before flinging the overhead out of reach. The crowd loved that one.

Marino holds on and it will be up to Boulter to serve out the opener.

After struggling early on, Katie Boulter is improving with each service game and she's looking a whole lot more confident now.

The 22nd seed wraps up a dominant hold and goes within one game of the first set with a booming ace, her first of the match.

And there it is. It's a dreadful game from Rebecca Marino, who hits another shot well beyond the baseline.

Just as her fiancé Alex de Minaur wraps up the second set over on Rod Laver Arena, Boulter goes a break up.

Image source, Getty Images

Yikes. A wild mishit from Rebecca Marino and all of a sudden Katie Boulter finds herself with three break points.

Alex de Minaur has just laid down another powerful ace to wrap up the second set.

The Australian broke Van de Zandschulp's serve to make it 6-5 and then hit two aces in his service game to clinch the set. He fist bumps towards his coaching team and lets out another massive roar.

Van de Zandschulp is fighting a bit better now, but too many unforced errors have seen him land on the wrong end of the set once again.

A half chance for Katie Boulter as Rebecca Marino double-faults and then finds the net. 0-30.

Jonathan Jurejko
BBC Sport in Melbourne

“Our Katie,” is how one Aussie steward just described Boulter.

Erm, I’m not sure about that.

Boulter might be engaged to Aussie hero Alex de Minaur but they aren’t stealing Britain’s leading women’s player.

It is easy to see Boulter’s popularity here. At gone 9pm there is still a very healthy crowd watching her.

One little girl is enthusiastically waving a homemade sign in the direction of Boulter.

The handwritten message split across four quadrants? ‘I Love You Katie!’

Image source, Reuters

After a double fault opens Katie Boulter's service game, we finally get ourselves decent rally. The British number one defends brilliantly, holding on until Rebecca Marino pushes the ball wide.

And another! Some quickfire net play and Boulter has a big smile on her face as she wraps up the point, and then the hold. The best game so far.

You might remember Rebecca Marino's name from November's Billie Jean King Cup Finals, when she lined up for Canada against Great Britain.

Emma Raducanu claimed a 6-0 7-5 victory over the 34-year-old, so Katie Boulter will be hoping she can do something similar today.

Image source, Getty Images

Rebecca Marino looks on course for a straightforward hold before a double fault halts her progress.

And the Canadian shows some nerve after missing her first serve at 40-30, going for broke with a brilliant second serve to get the hold over the line.

Daniel Kiernan
Former British tennis player

I guess Katie Boulter is at the peak of her career right now. She is at her peak moment, you can feel it, after obviously having many injuries and not being able to get her tennis quite to this level in the early stages of her career.

But she has now got a four, five or six-year window where she can really push on and I think she can push on even further as well.

She has shown some fantastic tennis over the past few months.

The net works in Katie Boulter's favour, stopping Rebecca Marino twice before the 22nd seed advances to push down a winner.

A backhand straight down the line wraps up the hold. That's much better from Boulter and we're all square again.

Image source, Reuters

There you go. Katie Boulter finds the fence with the first one, but she ends the next point with a clenched fist as Rebecca Marino fires long with a looping forehand.

Better from Boulter, but she needs to back it up to level this first set.

Now then, what can Katie Boulter do here? After that disappointing service game, the British number one finds herself with two break points to get back on serve.

Botic van de Zandschulp has just fumbled two set points on De Minaur's serve!

The world number 84 failed to capitalise at 30-40 with a long forehand, then he followed it up with a forehand down court and into the net at advantage on deuce.

De Minaur had one chance to see out his service game and he took it at the first time of asking, letting out an enormous roar after managing to pull through a bit of danger.

Image source, Getty Images

Ah, a dreaded double fault.

It's not the best start for the British number one and she's got a lot of work to do now as Rebecca Marino gets the early break.

But just as soon as Katie Boulter saves the break point, Rebecca Marino has another. What can she make of this one?

Katie Boulter definitely needed that one. A forehand winner down the line saves the break point and pulls us back to deuce.

Katie Boulter can't make the most of that advantage and she pays the price as she sends the ball into the net to give Rebecca Marino the first break point of the match.