Australian Open champion Angelique Kerber is one set up against Misaki Doi and has taken a 3-0 lead in the second.

And she's just put herself forward as a shot of the day contender.

Tracy Austin
Former Wimbledon mixed doubles champion on BBC TV

Cibulkova is timing the ball beautifully today, not taking a step back.

Radwanska feels the need to up the ante a little bit, go for a little more.

Dominika Cibulkova has taken the first set against Agnieszka Radwanska. Here's one of her winning shots. 

Image source, Getty Images

Britain's Katie Swan is out of the girls' singles after retiring midway through her first-round match against Georgia's Mariam Bolkvadze. The 12th seed was losing the first set when she withdrew.

Mike Henson
BBC Sport at Wimbledon

Image source, BBC Sport

Is that the sound of a bandwagon creaking?

Up in swanky Wimbledon village, the eateries and boutiques are digging the tennis decorations out of storage for another fortnight to try lure some of the tennis championships' human traffic their way.

Full marks to one ladies clothes shop for not taking the whole thing too seriously.

Tracy Austin
Former Wimbledon mixed doubles champion on BBC TV

A sign of nerves there from Cibulkova. Three quick errors in the last three points.

Cibulkova had two break points for a double break in the first set during the last game.

Chris Ward: Has to be either The Chain (for the F1) or Soul Limbo (for TMS). Both utterly iconic, but also different.

Laura Cooney: Fave sports theme tune: Wimbledon closing music or (traitorous as this sounds) 'Soul Limbo' - TMS. Both sound like summer to me.

Mark Simmonds: Have always loved the BBC Snooker theme tune, apparently officially called "Drag Racer" by the Doug Wood Band. Who knew?

Dominika Cibulkova has raced into a 4-1 lead in the opening set against Agnieszka Radwanska.

Third seed Agnieszka Radwanska and Dominika Cibulkova are up and running on court three - you can watch the fourth-round match here. 

Slovakia's Cibulkova has already got an early break. 

She's the one who is an expert tennis ball sniffer (see below for clarification).

We asked you for your favourite TV sports theme tunes:

Jonathan Frewen: Got to be Fleetwood Mac's Chain - Formula One/Grand Prix theme.

Adam Barras: My favourite theme has to be @fleetwoodmac, external 'The Chain' for @bbcf1, external it gives me goosebumps every time!

The man behind the music - Keith Mansfield - is a special guest at SW19 today.

The composer has come up with all the classic BBC sporting themes - including Grandstand and Wimbledon.

You know the one? "Do do do do do. Do do do do. Do do do doooooooooo."

So we want to know what your favourite sporting theme tunes are.

Is it the Wimbledon one? The cricket calypso? What about Ski Sunday?

Let us know via #bbctennis on Twitter. 

Seven-time champion Roger Federer plays American Steve Johnson, the current world number 29, at 13:00 BST.

Jonathan Jurejko
BBC Sport at Wimbledon

Image source, BBC Sport

If someone who cared little about tennis walked into Wimbledon Park today, even they would realise the Andy Murray show is in town. That's despite a definite lack of visible union jack support in the famous queue. 

The snaking line has lengthened considerably as patient punters wait for a grounds pass and - fingers crossed - bag a picnic spot on Murray Mound later. That's the prize all those I've spoken to have their eye on. 

Turning up now gives you a queue number creeping into the early 8,000s. Eek. But the good news is they *should* be walking through the gates about 14:30 BST - well before Murray's match of the day against Nick Kyrgios.  

Quick, turn on BBC Two. Sue Barker's there to bring you all the action from Manic/Magic Monday.

Britain's Katie Swan lost in round one of the ladies' singles last week but the 17-year-old is seeded 12th in the girls' competition.

She started her juniors campaign at 11:00 BST on court 16 against Mariam Bolkvadze of Georgia.

It's going with serve at the moment. 

Image source, Getty Images

I think Jo-Wilfried Tsonga was pretty happy about winning yesterday.

He's back in action today in the last 16 against fellow Frenchman Richard Gasquet. 

There's a plaque which has been erected on the side of court 18 here at Wimbledon to commemorate the longest match ever in the tournament.

John Isner beat Nicolas Mahut 70-68 in the fifth set here six years ago.  The match lasted 11 hours and had to be played over three days.

And we thought history was repeating yesterday.

Isner and Jo-Wilfried Tsonga entered a lengthy battle in the deciding set in their third-round match on court two. 

This time, though, it ended with Tsonga winning 19-17 in the fifth and the match only (!) lasted four hours and 24 minutes.

Here are the highlights: