That was a rank service game from Angelique Kerber.

 A couple of forehand duffers are followed by a double fault to surrender her serve to 15.

A really competitive affair with twists and turns, ups and downs.

Image source, AP

The sun is out, so it's got to be time for a selfie, right?

Dame Kelly Holmes, Olympic 800m and 1500m gold medallist at Athens 2004, gets in on the act.

Did you know? Selfie sticks are banned at Wimbledon. It's an actual fact.

Image source, Reuters

Lindsay Davenport
Former Wimbledon champion on BBC TV

This has been some of the highest quality we have seen, off the ground, the movement, the gets, the shot selection. 

Impressive stuff from both early on.

This is some grade-A 100% proof tennis.

Angelique Kerber is hitting from a more solid platform, getting her feet set and flipping over some fiery forehands.

But Simona Halep is covering every blade, chasing like an over-eager Labrador.

Eventually the German runs down Halep's defence and steals another game against the head.

Image source, EPA

Tracy Austin
Former Wimbledon mixed doubles champion on BBC TV

Shvedova is a very good athlete and has a big serve. She has the ability to move forward.

Image source, Getty Images

Actress Sienna Miller looks super-cool in the sunshine after taking her seat in the Centre Court Royal Box.

Image source, AP

Lindsay Davenport
Former Wimbledon champion on BBC TV

There is no question Halep is one of the fittest players out there, she works very hard.

But the expectation, we have seen it get to her on court in some of the bigger matches she has played in the last couple of years.

Image source, AP

Jonathan Jurejko
BBC Sport at Wimbledon

Image source, BBC Sport

Earlier today Roger Federer was down on the practice courts. Looking as cool as a cucumber that has been left in the fridge for two weeks obviously. Fans lined up against the fence, peering through the mesh to see their hero go through the paces. 

While a relaxed Fed swatted a few smooth-as-silk backhands over the net, his quarter-final opponent Marin Cilic was also prepping just a cheeky lob away on the adjacent court. Coach Goran Ivanisevic - the 2001 champion of course - had his beady eye on his man, leaning in now and again with a few words of wisdom. 

Image source, BBC Sport

Image source, Getty Images

She's still got it.

Martina Navratilova - a winner of 59 singles and doubles Grand Slam titles - and Tunisian Selima Sfar have put away the all-Czech duo of Jana Novotna and Helena Sukova 6-1 6-2 in just 50 minutes in the invitational doubles.

If you missed Just Call Me Martina by the way, you can catch it on the BBC website. Well worth an hour of your time.

Simona Halep -a scurrying chaser of a player in the mould of Arantxa Sánchez Vicario - snaps straight back at Angelique Kerber, hustling the German fourth seed out of her serve to love.

Angelique Kerber catches a backhand sweet as a nut down the line to force her way to 30-30. Simona Halep just watches it skid by.

The German is hitting with nagging depth, forcing Halep back towards the Royal Box. Halep now has some lateral movement to deal with as Kerber strokes across court.

She claws back over the net but wide. First blood Kerber.

Put your lunch break to good use today by sampling our wealth of Wimbledon video. If you've had your break - it's still fine to watch the videos. Your boss will probably be doing the same. Probably.

Over here...

Lindsay Davenport
Former Wimbledon champion on BBC TV

Great start for Kerber to settle any nerves that might be there. 

Both players are going to work hard on their service games. There won't be a lot of free points with that shot it is more about placement.

Image source, Getty Images

Jonathan Jurejko
BBC Sport at Wimbledon

As a barely-sweating Roger Federer swigs a glug of water at the end of his session, he looks up to see a familiar face breeze past. It's Andy Murray! 

The pair don't exchange glances, Murray fully in the zone as he heads back inside. No sign of Ivan Lendl though, Jamie Delgado is responsible for carrying about a dozen spare racquets. 

Can't imagine practice for the British number one is that bad that he breaks loads...

Image source, BBC Sport

Tracy Austin
Former Wimbledon mixed doubles champion on BBC TV

Halep got to the finals of the French Open, semi-finals here and she is more diminutive.

I love to watch her play. She is speedy around the court, not a big serve but accurate and she is so fluent with her groundstrokes.

This to match for me is right at 50 50, it really intrigues me.

They have experience at four and five and in the world - there is so little between them.

Image source, AP

Lindsay Davenport
Former Wimbledon champion on BBC TV

These are two of the best athletes in the women's game.

They are also two players who prefer defence rather than offence, it will be interesting to see who steps up to take more chances. 

Simona Halep and Angelique Kerber are out warming up on a sun-drenched Centre Court.

This is the first time the pair have met on grass.

Romania's Halep reached the semi-finals here in 2014 while German Kerber is hoping to add to the Australia Open title she won earlier this year.

Russell Fuller
BBC tennis correspondent at Wimbledon

The draw has taken place for the first ever wheelchair singles event to be staged at Wimbledon.

The US Open champion Jordanne Whiley will meet Lucy Shuker in an all British quarter-final, and the current Australian Open champion Gordon Reid, from Scotland, will play Nicolas Peifer of France.

Standing in the way of Williams in her 12th Wimbledon quarter-final is Anastasia Pavlyuchenkova.

The Russian world number 23 has never made it to the last eight before at Wimbledon.

Here's how they match up

In the rather wonderful 'Serena' documentary which was broadcast on Monday night, women's single legend Billie Jean King was filmed giving a pep talk to Ms Williams and she said "pressure is a privilege". 

Since winning here last year, Williams has been one Grand Slam away from matching the Open Era record of 22 - held by the legendary Steffi Graf.

If that isn't pressure, I don't know what is.

Image source, AFP