Jeff Tarango
Former American tennis player on BBC Radio 5 Live

Mensik looked defeat in the face and just wasn't going to take it. In the last six points he has played unbelievable tennis.

In the last month and a half, Mensik has been playing like a top 10 player so the seeding doesn't reflect what the locker room thinks.

Dom Inglot
Former British tennis player on BBC Two

I think Mensik is trying to rush it a little too much, which is credit to the speed of Samuel, who is defending very well.

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Jakub Mensik receives a time violation for taking too long before his first serve.

The Czech 15th seed doesn't let it affect him as he seals the game with a big first serve, despite a magnificent passing shot from Toby Samuel on the previous point.

Alexander Blockx almost follows winning the second set by breaking right at the start of the third, but Alexander Zverev recovers from 0-40 down to hold serve.

Zverev began with two double faults in that game.

Blockx holds to level the set.

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Jakub Mensik shows his class as some consistent deep striking sees the Czech 15th seed get the better of a couple of rallies.

The pressure is on Toby Samuel a bit now and it shows as he goes wide with a forehand and offers two break points.

Samuel saves one but can't rescue the second as he's unable to control a powerful stroke and his forehand spoons long.

Tim Henman
Former British number one on BBC iPlayer

The quality of Zverev's serving has been outstanding.

No double faults [before that set point] and had been serving at 110mph plus on the second serve, but it proved costly on that occasion.

You feel like Zverev has probably been the better player but until you get the break of serve or get that opportunity in the tie-breaker to finish it off, it can prove challenging.

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Toby Samuel is not letting up as a passing shot down the line proves too good for Jakub Mensik.

The Czech 15th seed battles back with a big first serve and an ace to hold and keep in touch in the deciding set.

Alexander Blockx gets to set point once more - and it's a double fault from Alexander Zverev!

He went big on the second serve and went just long.

All square on Centre Court.

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Ryan Harrison
Former French Open men's doubles champion on BBC Two

Blockx is getting a lot better read on the serve in the tie-break than he did in the previous return game - where Zverev had four aces - and now he is starting to get a feeling of where Zverev wants to return.

Backhand down the line goes well out from Alexander Blockx.

Toby Samuel has the break of serve in the deciding fifth set against Czech 15th seed Jakub Mensik.

You can feel the excitement from the crowd, who are sensing a potential upset here, but Samuel looks cool as a cucumber as he takes his seat before the change of ends.

Samuel, who is making his debut at Wimbledon, then backs up the break with a hold. One step closer to the second round...

Alexander Blockx finds the passing winner!

Another set point, this time on his own serve.

Alexander Zverev hits the line with a groundstroke and Alexander Blockx mishits his next shot out.

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Serve unreturned - now the Belgian has a set point on Alexander Zverev's serve.

The chance was there for Alexander Zverev but the backhand pass down the line hits the net and stays on his side of the court.

A serve and volley from Alexander Zverev at 5-5 and he earns a set point for a two sets to love lead.

Britain's Billy Harris has been broken and is down 4-1 in the fourth set of his match against Russian 19th seed Karen Khachanov.

You would expect Khachanov, who is a two-time quarter-finalist at Wimbledon, to go on and win from here but stranger things have happened.

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Alexander Blockx moves a mini-break in front with a cracking backhand winner, but can't back it up and loses the next point on his own serve.

It's back on serve now and any sort of error on serve now will surely be pivotal.

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Otto Virtanen, speaking after his five-set victory over fourth seed Ben Shelton: "I don't know if I have a heart any more. I think it bounced out of my body but I'm here, I played until the last ball.

"I had a great month before this, I played a lot of grass matches and I've always enjoyed playing here. Last year I missed because of injury but two years ago I had a great time here and it feels so good to be back."

On coming back from injuries and setbacks: "It definitely means a lot to my life to get a big win on a big court in my favourite place so, just after having a tough year also, playing good but not getting good wins and again getting a lot of injuries and I was sick a lot.

"Playing now every day for one month and feeling healthy, playing thinking the results will come and now here we are."

A couple of superb volleys at the net earn Alexander Zverev the first mini-break of the tie-break.

Zverev then plays a drop shot during a lengthy rally and a slip from Alexander Blockx proves critical.

But then Blockx gets the mini-break back with a powerful second-serve return that Zverev can't get back, before holding serve on his next two points.