Over on our BBC Sport Facebook page, external there's been some musical fun and games with Keith Mansfield, who's written many famous sporting themes like Grandstand, Wimbledon, external and more...

He's going to hum the songs, and we want YOU to guess the tune...

John Lloyd
Former British number one

Image source, Getty Images

It's a such a pity. Kei Nishikori gets so many injury problems. In Japan he is a megastar beyond belief. It's a tennis-mad country - boy do they support the sport financially. He can't go anywhere without being mobbed.

Cilic has broken Nishikori for a second time after the fifth seed broke the Croat

Image source, Getty Images

There are a host of sporting stars in the Royal Box as well. Danny Willett - Masters champion - is sporting a green jacket. It looks a lot like the green jacket that Jordan Spieth hung on his shoulders at Augusta as well.

Masters champions get to keep that garment for a year before returning it to the Augusta clubhouse on their return. So you can't blame Willett for giving it an airing when he can. He probably takes the bins out in it even.

You know you have hit a good shot when Roger Federer applauds you. 

Federer has taken the first set against Steve Johnson though.

Roger Federer is never short of support at Wimbledon, but he'll be cheered to see his wife Mirka, left, in the crowd today. She is sitting near US Vogue editor Anna Wintour (centre).

Image source, AFP

Marcus Willis
Great Britain tennis player, who lost to Roger Federer in the second round

Roger looks good - I can vouch for that. 

It has taken him a few games but he is on a roll now.

Roger Federer smacks a clean-as-a-whistle winner down the line en route to a break and the first set.

Meanwhile in the BBC One commentary box Jim Courier tells an outstanding anecdote about Steve Johnson's competitive instincts being confirmed to him by the younger man's emphatic victory in a US Davis Cup team hotdog eating contest.

Image source, EPA

Mark Petchey
BBC Sport

There were 12 aces in that set for Marin Cilic. It was as comprehensive as the scoreline suggests.

Number five seed Kei Nishikori appears to be suffering from illness or an injury

Image source, EPA

Jim Courier
Former world number one on BBC TV

Federer has a quizzical look on his face - he's wondering what kind of player he is up against. Steve Johnson has a unique style.

Image source, PA

Marcus Willis
Great Britain tennis player, who lost to Roger Federer in the second round

Roger made it pretty difficult for me.

He got a lot of balls in, he was very solid.

I thought I played all right just not winning the main points and that is where Roger is very good.

Frank Keogh
BBC Sport

Wimbledon is famous for its strawberries and cream, so I guess if you're doing fancy dress....

Tennis fan Chris Fava has travelled more than 5,000 miles from his home in Venice Beach, California, to visit what he calls "the hallowed ground" of SW19.

"Venice Beach is crazy, but this is bananas," said the 40-year-old dressed as a strawberry. "This feels like home."

Image source, BBC Sport

This is not the creative director's first time in fancy dress at Wimbledon, but he ran out of weather options after coming as:

2013: 'Sky Man'

2014: A daisy

2015: 'Mister Sunshine'

It's first blood Federer on Centre Court.

The Swiss seven-time champion breaks the serve of American Steve Johnson to gain the upper hand in the first set.

Frank Keogh
BBC Sport

Big day for the USA - six of the 32 players in the fourth round of the men's and women's singles are American. And it's American Independence Day.

Women

Madison Keys is on Court One right now, playing Simona Halep, while Venus Williams v Carla Suarez Navarro follows.

Serena Williams is second on Centre Court, against Svetlana Kuznetsova, while Coco Vandeweghe was defeated earlier.

Men

Steve Johnson is currently trying to score a shock success for the stars and stripes on Centre Court against seven-time champion Roger Federer. Novak Djokovic's conqueror Sam Querrey is playing Nicolas Mahut on court 18.

Mark Petchey
BBC Sport

How long Kei Nishikori wants to go through the agony... he's clearly not 100%

Third seed Agnieszka Radwanska - a finalist here in 2012 - has fought her way back into her fourth-round match against 19th seed Dominika Cibulkova.

The Slovak was serving for the match but Radwanska broke and then went on to take the second set.

If Cibulkova does progress into the final, it could cause some problems with her diary,

She's meant to be getting married on Saturday...

Mike Henson
BBC Sport at Wimbledon

Image source, BBC Sport

Andy Murray and crew cast anxious glances over towards the entrance to their practice court. It would be a brave junior who would demand their prompt exit though.

Still enough time for Jamie Delgado to step up to the service line and bash down some full-pelt serves in an attempt to replicate the Kyrgios tee-off.

Marcus Willis
Great Britain tennis player, who lost to Roger Federer in the second round

Life is really good, I've not had a whole lot of sleep.

It is a bit weird. People are asking for photos of me and I'm not very good looking.

The atmosphere was incredible when I played Federer.

Richard Krajicek
On Radio 5 live at Wimbledon

In his first match Federer's movement was not impressive at all and I didn't think he could make the semi-finals but against Marcus Willis he was really moving so much better.

It was incredible to see the improvement in two days and against Dan Evans he maybe even moved better.

Image source, Getty Images

Jonathan Jurejko
BBC Sport at Wimbledon

Image source, BBC Sport

Djokovic-slayer Sam Querrey has taken up more newspaper column inches in the past couple of days than he had in the previous decade. Now it's time to find out whether he has floated down from cloud nine. 

The American 28th seed is about to face France's Nicolas Mahut, the doubles specialist who is through to the last 16 for the first time. 

Querrey bounds out to a healthy applause as the court 18 crowd take their opportunity to applaud his win against Djoko. Most of them must be Murray fans.