Play is about to start on the two main courts.

On Centre Court...

It's a pretty high level out on court 18. British teenager Jay Clarke and Ernests Gulbis are giving the ball a beating.

Both players are playing some of their best stuff and Clarke is right in this match. He's bouncing around at the back of the court as he waits for his opponent to serve.

Here are a few highlights from the second set...

This time it's Johanna Konta who fires long.

Fist pump from Natalia Vikhlyantseva. She's broken the British number one out of nowhere.

Natalia Vikhlyantseva goes long with her return and Johanna Konta saves the first.

The Russian catches the breeze off her next effort and she's down to one chance.

Jo Durie
Former British number one on BBC TV

Not sure Konta needs to be to clever, just get the basics done. The drop shot didn't quite work.

Collective sigh of disappointment. That's the challenge facing British players at SW19... Konta gets one after a miscued drop shot. "We're not angry, just disappointed," say the crowd.

A double fault follows and suddenly Natalia Vikhlyantseva has three break points.

Del Potro has doubled up.

After a mini-wobble where he had to save break points, the Argentine raced through the final two games to take a two set lead. Just three unforced errors for the sixth seed in that set.

Kei Nishikori has never had the happiest of times at Wimbledon, failing to make it past the fourth round in his nine previous efforts.

He's in a spot of bother on court 14.

American Christian Harrison takes the second set against the former world number four.

Natalia Vikhlyantseva is scrambling and saving, pulling out the big strokes when in need.

She saves two break points to keep the difference at one break in Konta's favour.

And now Konta is staring at a second break in this set.

She coaxes a return off the top of her frame and Natalia Vikhlyantseva saunters in to save.

Cracking low-bouncing backhand from the British number one from deep.

Another break point.

Finally Johanna Konta cleans up with a whipping backhand along the line that swerves inside the baseline at the last second.

She holds.

Image source, Reuters

Johanna Konta responds to the racquet-wrecker by firing in a body serve like an angry fast bowler.

The Russian fights back with venom of her own. Deuce. Chance for Natalia Vikhlyantseva? Nope. She drags a backhand a long way wide off her frame.

That's better from the 21-year-old though, zipping a low forehand into Konta's path as the British number one heads to the net and we're back to deuce.

We've got a serious match on now on court 18.

Ernests Gulbis' winner count is rising and a couple more heavy blows help him take the second set.

Jay Clarke still looks calm as he sits in his chair but the 19-year-old has got work to do if he's going to win on his Grand Slam singles debut.

Watch here.

A brief wobble from Juan Martin del Potro, who finds himself two break points down.

He rallies to win four points in a row and keep proceedings on serve. Delpo's hit 20 winners today, to Gojowczyk's 9.

Jo Durie
Former British number one on BBC TV

I think Konta is in control of this match, but there is still an edge to it, her opponent can hit some winners so she is being very focused.

Johanna Konta deals with a return that clips the net and falls short by dancing around the bounce and lashing it into the hoardings behind Natalia Vikhlyantseva.

The British number one slaps her next backhand long, and then is knocked off balance by a meaty Natalia Vikhlyantseva return -15-30.

This is how Konta earned her second break point against Vikhlyantseva.

Judy Murray is on a mission - to get more women and girls playing and coaching tennis across the UK.

Here she is at one of the 'She Rallies, external' sessions in Galashiels recently...

You can find out more about how to get into tennis with the Get Inspired guide.

Well, Natalia Vikhlyantseva has certainly served well today. The Russian is finding some serious punch off the heart of her racquet, but having fallen 40-0 behind, Johanna Konta gets to grips with the world number 103's power and takes successive points.

Vikhlyantseva mixes it up, strides into the net and steams a half-volley beyond the Brit to hold.

Ernests Gulbis has hit some form against Jay Clarke. After a messy start the Latvian is now firing on all cylinders.

He's serving for the second set and the chance to level this match.

Watch here.