A mountain to climb for Henry Searle now.

The former boy's singles champion did well to hold off Ethan Quinn on his last service game, but he can't do the same again.

With unforced errors spraying off his racquet, Searle's challenge looks to have wilted as he goes a double-break down in the fourth set.

Carlos Alcaraz is surely closing in on victory now!

Fabio Fognini races into a 40-0 lead, looks in great touch and then it all just falls away.

Alcaraz gets it back to deuce, earns one break point that Fognini manages to save but the Italian then nets a backhand to give him another.

The defending champion takes it this time and is just two games away from a place in round two.

Harriet Dart responds well to losing the second set, holding to love in the opening game of the deciding set.

Her sweeping forehand wrongfoots opponent Dalma Galfi and the crowd cheer to show their encouragement for the British number four.

Anne Keothavong
Former British number one on BBC Two

I know Mimi Xu has been working hard on her serve and her forehand.

She possess a fairly flat forehand but it used to be even flatter, so we are seeing more shape on her shots now. She wants to adopt an all-court game and we are already witnessing that this afternoon.

In terms of her development, she is still a work in progress but she has the tools, mindset and work ethic to do well.

The quality of Emma Raducanu's first serve is standing out to me. She has won 100% of points behind her first serve - with a 68% first serve percentage - and if she continues in that form then she will be very tough to break.

The unforced error count is quite high for Mimi Xu, so she just needs to clean up on a few things there.

Emma Raducanu takes the first set in 37 minutes as, on set point, Mimi Xu goes wide with a forehand.

Xu has settled as the match has gone on but Raducanu has been the better player, especially on her serve. Every time she has got her first serve in, Raducanu has won the point.

Jonathan Jurejko
BBC Sport senior tennis reporter at Wimbledon

The spectator is carried out of Centre Court by paramedics on a chair, drawing a sympathetic round of applause from the crowd and the players.

After a wait of almost 15 minutes, the match gets back under way.

Almost bad to worse for Henry Searle.

The British wildcard had to fend off another break point in the third game of this fourth set, but battled back to secure an important hold against Ethan Quinn.

He is not completely out of this yet, but will need to try and get the early break back if he is to push this into a deciding set.

Tim Henman
Former British number one on BBC One

Carlos Alcaraz has set the bar for his performances so high because his form has been absolutely sensational.

But his first serve percentage has been rather low in this game, it has been around 50% so Fabio Fognini has been getting plenty of chances to attack the second serve.

The unforced errors have continued to flow as well, so there hasn't been a great deal of rhythm which is so rare for him.

Carlos Alcaraz gives a thumbs up and begins warming up which suggests there is positive news regarding the fan on Centre Court.

There is applause as the fan is helped away from the court and, after a brief chat, the players decide they don't need another warm-up.

We're ready to go again after a break of a little more than 15 minutes. Fabio Fognini, a break now in the fifth set, to serve.

Just like that, Dalma Galfi win two consecutive games to love to take the second set.

British number four Harriet Dart became increasingly frustrated, with several shots which were wide of the target, and almost seemed to concede defeat.

We will have a decider and I think it will be rather difficult to call the winner of this match.

Emma Raducanu lets out a huge roar when Mimi Xu sends a return long at 30-30.

Another Xu forehand sails over the baseline on the next point and Raducanu is one game away from winning the opening set.

Image source, Getty Images

Sam Smith
Former British number one on BBC Two

Mimi Xu seems to have settled down very quickly after that nervy opening service game.

That was her best service hold so far and the 17-year-old wildcard is staying in touch in this opening set.

Not how Henry Searle would have been hoping to start this fourth set.

The 19-year-old has gone down a break in the opening game and it is now a long way back if he is to overturn this deficit to Ethan Quinn.

A lightning-quick hold to love from Mimi Xu keeps her in contention in this first set.

The next challenge is to find a way to break Emma Raducanu.

There have been some long games in this match and we have just come through another.

Dalma Galfi holds on her service game with two consecutive aces as she goes ahead in the second set.

Jonathan Jurejko
BBC Sport senior tennis reporter at Wimbledon

Play is stopped on Centre Court as stewards and medics help the stricken spectator.

Carlos Alcaraz hovers around that side of the court, looking very concerned and regularly checking what's happening.

Fabio Fognini chats to British umpire James Keothavong in the shade near his chair.

Fingers crossed the spectator, who is being sheltered by two Wimbledon umbrellas, recovers quickly.

Emma Raducanu is playing very smartly in the early stages - she's staying in points, not trying to be overly ambitious and just waiting for the error to come from Mimi Xu.

More often than not, it has done, although Xu hits a forehand winner to secure her first point on the Raducanu serve.

A hold to 15 for Raducanu, who still leads by that early break.

Image source, Getty Images

Jess Anderson
BBC Sport at Wimbledon

That incident on Centre Court is a reminder that even as we approach the evening the temperatures out here are still pretty sweltering.

Mercifully, much of Court One is now in shade but there is still one unlucky corner bathed in sunshine.

It's a slog in the direct heat, for sure.

Harry Poole
BBC Sport at Wimbledon

Harriet Dart had to dig so deep there to come through four break points - but the fifth proves one too many.

A third consecutive break of serve leaves the second set in the balance.

Cheers of ‘Come on Harriet’ rise up around court 17, situated between the grand walls of Centre Court and Court One.

The Briton is still a set to the good, but there’s a lot of battling still to do in these testing conditions.