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Andrey Rublev, who is 14th seed, lost in the tie-break in the first set againt South African Lloyd Harris, but has since won two sets and is leading the fifth set 3-2.

Karen Khachanov is leading 4-3 in the fifth set against Shintaro Mochizuki.

Billy Harris hits a forehand right into the corner with Nuno Borges just unable to reach it.

The crowd cheers as they do their best to encourage Harris.

"Come on!" roars Katie Boulter as she breaks back.

Solana Sierra saves the first two of the break points but Boulter's fierce backhand is too much for her on the third.

Back on serve in the first set. Can Boulter ride this momentum now to take it?

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Carlos Alcaraz makes no mistake, finishing with an ace to take the second set.

Like the first, Ollie Tarvet was well in contention but he'll rue a poor serving game at 4-4 that proved costly.

Billy Harris wins the first two points in the tie-break before hitting into the net under pressure from Nuno Borges.

The crowd are up now.

Katie Boulter is coming out fighting and has three break points as Solana Sierra slaps a forehand into the net.

0-40.

Nuno Borges does force a tie-break to decide the third set.

All or nothing for Briton Billy Harris if he is to stay in the match.

The crowd gets behind Katie Boulter as she holds to love.

She's not been anywhere near her best yet and the big-hitting Solana Sierra is growing in confidence.

The Argentine will now serve for the first set.

Billy Harris continues his fine form in the third set.

He holds on his service game with an ace as Nuno Borges can only return long.

Borges will serve as he tries to force a tie-break.

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Carlos Alcaraz takes a giant stride towards winning this second set with a crucial break.

Ollie Tarvet's serve deserted him at the worst possible moment, with the Spaniard taking the first of three break points to go a break up.

He'll serve for the second set in a few moments.

Gary Rose
BBC Sport at Wimbledon

A little bird of some description has a think about landing on the court as it flutters about but thinks better of it and opts to get a good vantage point on the edge of the roof.

After Cameron Norrie's brilliant win on this court a little earlier, there's a few empty seats around Court One at the moment, but Katie Boulter could do with the support as this first set is going away from her.

Katie Boulter has an opening at 15-30 but Solana Sierra finds something extra on her serve to claim the hold.

Boulter manages to get one big serve back but is then off balance as Sierra powers a backhand past her.

Impressive stuff from the lucky loser and Boulter has it all to do to try and rescue this first set.

Naomi Broady
British player on BBC Radio 5 Live and BBC Sounds

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This is quite a struggle, Solana Sierra is returning very well. The crowd are trying to lift Katie Boulter, she's far from her best here and I think she's going to have to up it somewhat.

Jonathan Jurejko
BBC Sport senior tennis reporter at Wimbledon

You can tell Ollie Tarvet is a star in the American college system from the exuberance he shows on the court.

Buckets of energy, lots of expression and plenty of entertainment.

The US collegiate game, known for its fun and noisy atmospheres, brings that out of its players.

This second set's going to the wire.

Ollie Tarvet can't put pressure on Carlos Alcaraz's serve, with the Spaniard holding to 15 to level at 4-4.

Worrying signs for Katie Boulter on Court One as another double fault hands Solana Sierra the break.

The Argentine had produced a brilliant forehand return, the ball smoked down the line and just clipping the baseline.

That put her up 15-30 before a tame forehand into the net from Boulter gave Sierra two break points.

The scoreboard might be against British qualifier Ollie Tarvet but he's had some great moments and is giving an excellent account of himself, as shown by this rally early on.

Oh Ollie Tarvet that is spectacular.

The young Brit has the Centre Court crowd on their feet with a stunning forehand cross-court winner that even Carlos Alcaraz had to appreciate.

He holds by reaching the Spaniard's crop shot and clipping a return back.

A booming serve from Billy Harris completes his service game with an ace.

For the first time in this match, Nuno Borges is the one on the back foot.

Those early nerves seem to have dissipated for Solana Sierra.

The 21-year-old races through her latest service game and holds to love when Katie Boulter's forehand flies long.