Sloane Stephens sends a volley, which you would expect her to make, long and that brings up game point. The first serve is out from Raducanu, but the defence is strong and a low backhand volley from Stephens finds the net.

Raducanu one game away from the win.

Stephens finds the line with a great shot and it's the third deuce of the game.

Raducanu is at 40-0, but brings Stephens back into it, not helped by her fifth double fault. Deuce.

Laura Robson
Former British number one on BBC Radio 5 Live

This will really be tough for Stephens to come back from a double break down in the third set.

Raducanu looks like she has just stepped up a gear.

Raducanu produces an attacking return and Stephens sends a backhand long.

That's 4-0 to Raducanu, two more games and it's round two for her.

If Stephens is to advance, she is going to have to fight back from a double break down to do so.

Break point Raducanu, for what would be 4-0.

Raducanu 15-30 up on the Stephens serve. A chance to slam the foot on the accelerator here and race ahead.

So what Sloane Stephens will we see from here on? The one who folded meekly in the first set, or the one who fought for everything and shone in the second set?

Laura Robson
Former British number one on BBC Radio 5 Live

It just feels like Emma's found a bit of a groove again from the back of the court.

She has realised she needs to keep peppering the backhand.

It feels like Stephens has taken a bit of pace off the ball and waiting for the Raducanu mistakes, while Emma is dictating the play.

Jonathan Jurejko
BBC Sport at Melbourne Park

Raw emotion pours out of Raducanu after almost every point.

There is a frustrated slap of the knee or a swipe of the racquet through the cool Melbourne air when she loses a point she can't believe she's lost.

When she wins a key point, the clenched fist and elbow move to down towards a raising knee.

Didn't Steps have a dance move like that in one of their videos?

A backhand drilled down the line from Raducanu and she thinks she has got the game in the bag and walks off towards her chair.

She has not got the sums right though and that was only for 40-15.

But Raducanu does win the game soon after and that's a 3-0 lead in the final set.

Russell Fuller
Tennis correspondent in Melbourne

Raducanu breaks early in the deciding set and hopefully that will be the incentive to race through the set like she did in the first.

She took her opportunities there.

Stephens goes wide and Emma Raducanu gets what could be the decisive break of serve in the American's first service game of the deciding set.

Raducanu will be in the second round if she holds her serve from here on in.

Break point Raducanu.

Laura Robson
Former British number one on BBC Radio 5 Live

There's a reaction after every point from Raducanu - either a fist pump or frustration.

This is a new experience for her - emotions are running high.

No leg drive from Stephens on the serve - both players looking a bit nervous

A fine rally from both players, with Raducanu testing the Stephens backhand. That was 15-30 on the Stephens serve, but Raducanu then nets for 30-30.

A scream of "come on" after Stephens dumps a backhand into the net to bring about game point for Raducanu and the Briton then produces a cross-court backhand winner after the American had misjudged a drop shot. Game, Raducanu.

Laura Robson
Former British number one on BBC Radio 5 Live

The first Grand Slam decider that Emma Raducanu's ever played.

I can't believe this is the situation. I have no stats to work with.

Both players left the court at the end of the second set, but they're back and we're good to go again.

It's a one-set shootout for a place in round two.

It's 11.20pm in Melbourne and another set to come. It's a late night for everyone there.

Some good early afternoon entertainment for those of us in the UK.