Miomir Kecmanovic gives Jannik Sinner the runaround to get to 30-15, sending the defending champion deep into one corner before slamming away a winner on the opposite side.

The Serbian is looking very comfortable on serve and gets the hold when Sinner's return lands long.

No sign of nerves from Jelena Ostapenko as she powers down some big serves and big groundstrokes to bring up three more set points.

When Dart gets into the rallies, she shows what she can do as she forces Ostapenko to hit more balls than she would like.

She saves the first set point but can't do any more as the former French Open champion holds her nerve and serves out the first set on Court One.

Image source, PA Media

Naomi Broady
Former British player on BBC Radio 5 Live

It's tough because Norrie hasn't been playing much. He took a bit of time off after the French Open and has only played Queen's since but lost in the first round there so, he hasn't got much grass-court tennis under his belt while his opponent has come through qualifiers.

Chris Bradnam
BBC Sport commentator on BBC Two

Well done, Harriet Dart! An ace secures the game after two set points saved.

I said she was a fighter. She is doing everything she can to hang in here - and it seems she is enjoying it.

Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Live

Kecmanovic is travelling nicely here and Sinner has made a couple of mistakes so, he's just got to hold off this opening fight

Cameron Norrie finally gets over the line in the first set as he overpowers Michael Zheng to win the tie-break.

The British 26th seed did it the hard way but he got there in the end.

Image source, Getty Images

Jannik Sinner defends the first with an ace and then comes up with some fine net play to save the second for deuce.

Already some ooohs and aaahs from the crowd as the Italian starts to work through his repertoire of shots.

Sinner goes on to get the hold. First test overcome for the world number one.

BIG hitting from Jelena Ostapenko.

There is little Harriet Dart can do when the world number 31 steps up and powers through her returns, and it gets her two set points.

Ever the fighter, the Brit saves both with some great defensive work.

Her first ace of the day askes the serve-it-out question of Ostapenko.

Miomir Kecmanovic gets a solid early lead against serve, leading 0-30, and it's made all the more impressive as he wins one of those points after returning a 131mph serve.

Jannik Sinner hits back but then plays a very loose shot and has two early break points to save.

Michael Zheng battles to keep the ball in play and it pays off as Cameron Norrie puts a backhand into the net on set point.

It feels tense on court two right now.

Image source, Getty Images

Michael Zheng saves a set point on serve with yet another forehand winner after a big first serve.

Zheng's forehand has been a weapon in this first set tie-break.

The American then misjudges a backhand however, and Cameron Norrie has set point on serve.

Miomir Kecmanovic loses the opening point on serve but dusts himself down and settles into a rhythm.

The Serbian matches Jannik Sinner's opening service game by sealing a hold to 15.

That'll help to calm any potential early nerves.

Harriet Dart could really do with bringing up her first-serve percentage here.

Jelena Ostapenko continues to punish her when she misses, but Dart showing what she can do when gets in the rally as a lovely cross-court winner secures her her first hold of serve.

Ostapenko continues to have issues with her ball toss and it could cost her some points if she runs out of time on the clock.

Still, she comes through and holds to force Dart to have to serve to stay in this first set.

Cameron Norrie's five point streak is ended by a forehand winner from Michael Zheng, who follows it up with two more big forehand winners.

Norrie's mini-break has been wiped out.

Off we go.

No messing around from Jannik Sinner as he races into a 40-0 lead.

Miomir Kecmanovic refuses to lose the opening game to love, though, and nestles a winner into the corner to win his first point, but Sinner wraps up the hold on the next point.

Pretty routine stuff.

Cameron Norrie loses the first two points but fights back to secure a mini-break of his own with some fine hitting as he works Michael Zheng from left to right.

A big first serve then sees Norrie go into the change of ends with a two-point cushion.

Image source, Getty Images

Chris Bradnam
BBC Sport commentator on BBC Two

The 'come ons' are coming thick and fast for Harriet Dart now.

There are more hands on hips for Jelena Ostapenko.

Harry Poole
BBC Sport at Wimbledon

A warm reception from the crowd greets reigning men’s singles champion Jannik Sinner as he walks out on to Centre Court alongside Miomir Kecmanovic.

The world number one fell victim to one of the biggest shocks at a major in recent years at the French Open, exiting in the second round despite leading Argentine Juan Manuel Cerundolo by two sets and 5-1 in the third.

That collapse ended a 30-match winning streak for the Italian, as well as his bid to become the second-youngest man to complete the career Grand Slam - winning all four major titles - after rival Carlos Alcaraz achieved that in Australia in January.

Despite the manner of his loss in Paris, and not competing since, Sinner will begin as the overwhelming favourite to win Wimbledon again in the absence of the injured Alcaraz, whom he overpowered in four sets in the final last year.

Image source, Getty Images

If you haven't had the opportunity to take a look at BBC Sport's incredible deep dive into four-time Grand Slam champion Jannik Sinner, then now is your chance.

It's a fantastic immersive article looking at his beginnings and charting his rise to the top of men's tennis.

Read more about Sinner here.

Cameron Norrie, serving to stay in the first set, comes through no problem at all with a hold to love.

Tie-break time.