It is impressive how effortless Elena Rybakina is making this look, she's getting in all the right positions and making all the right shots.

Katie Boulter celebrates taking a point off Rybakina with a solid groundstroke but is the only celebration as Rybakina holds.

Matteo Berrettini wins a challenge as a Zverev forehand is proven to be long. That gives the Italian the mini-break in the tie-break once again.

A massive forehand follows and Zverev balloons a return wide to give Berrettini three match points.

Sam Smith
Former British number one on BBC TV

The defending champion is in complete control. There are very few openings for Boulter.

An excellent drop shot prompts a beaming smile on Katie Boulter's face - she needed that.

It clearly gives her encouragement and she takes the next point before hooking a good shot at the net out of Elena Rybakina's reach to lead 40-15.

Rybakina then sends her return from Boulter's serve wide and that's an important hold for Boulter.

After so much dominant serving from both players, the tie-break begins in bizarre fashion as serve is broken on all four of the opening points.

A Berrettini challenge fails as a Zverev forehand clipped the baseline, then the German makes errors on both his service points, before Berrettini double faults.

Normal service finally resumes with a Berrettini ace. All square at change of ends.

Elena Rybakina backs up the break with a hold and she leads 2-0 in this second set.

It is all looking a bit too easy for her out there.

But Elena Rybakina is nailing her first serve - she is yet to drop a point off it and she hauls herself back to lead 40-15.

Better!

A rally ends with Elena Rybakina sweeping a shot into the net and that prompts a huge roar from the home crowd.

A second tie-break in as many sets on Court One.

Alexander Zverev must win it to stay in the match.

Katie Boulter will feel like everything is against her as a Elena Rybakina's forehand clips the net and just drops over.

Rybakina has two break points and another shot into the net by Boulter gives the defending champion the opening game of this second set.

Jonathan Jurejko
BBC Sport at Wimbledon

The impromptu applause which came before Boulter served at 40-A 1-4 summed up the mood, really.

Backs to the wall stuff.

By the time Rybakina wrapped up the set, the noise had turned.

Shocked chatter.

This was not the script the British had hoped for.

Alexander Zverev holds to love for the eighth time in the match. Matteo Berrettini replies with a hold to 15, aided by a wasteful volley at the net from his opponent.

After that little blip of break points and deuces, the serves are back on top. One last chance for Berrettini to wrap the match up without the need of a tie-break.

The mistakes are creeping in as perhaps the size of the task facing her suddenly weighs down on Katie Boulter.

An unforced error is followed by a double fault and she is in danger of facing an early break here.

Anne Keothavong
Former British number one on BBC TV

She has given Katie Boulter no time to breathe out here. It was a faultless set of tennis from Rybakina.

Sam Smith
Former British number one on BBC TV

An utterly dominant set of tennis.

Elena Rybakina seals it with a second-serve ace.

An incredible first set by the defending champion, who did not put a foot wrong as she takes it in 26 minutes.

It would be hard for anyone to live with Elena Rybakina in this form and within the blink of an eye she has three set points.

Anne Keothavong
Former British number one on BBC TV

The ball speed and heavy ball striking of Rybakina is just too much for Boulter right now.

And Elena Rybakina seals the double break and is serving for the first set.

Elena Rybakina takes the next two points, the power of her shots making life difficult for Katie Boulter and the defending champion has the chance for a double break...