Plenty of hats on heads on a sunny day at Wimbledon but at what point does the weight of the hat outweigh the benefit of the sun protection?!

Image source, BBC Sport

Here we go then, Philipp Kohlschreiber to begin the second set.

And he wrong-foots Djokovic superbly! The Serb has to check back to meet a reverse forehand and lets out a groan in desperation, that'll check if he's properly warmed up.

1013IHaveatheory: What's been going on with the mowing on No1 Court lol

Dave Cooper: What's the issue/cause/change to the way the grass is cut this year compared to Centre Court - it looks strange?

Novak Djokovic only needs one. Philipp Kohlschreiber punches long and Djokovic takes the opening set.

Lovely stuff from the defending champ, sticking a forehand winner beyond the German.

Two set points.

Now it's Novak serving for the first set.

Djokovic opens up his body to meet a swerving return and hammers it home with a swivel from should height. That gets Centre Court going.

30-15.

Image source, Reuters

Soonwoo Kwon usually plays on the Challenger Tour - this is his first match on the main tour this year - but he looks at home on these lush lawns, and continues to go toe-to-toe with Russia's 10th seed Karen Khachanov.

Just as I write that, however, Khachanov conjures up a stunning backhand passing shot to break at the start of the second set, and he now leads 7-6 2-1. Still a lot of work for him to do to finish this one off though.

Novak Djokovic goes wide with a backhand, stares at it longingly but decides not to challenge.

Kohlschreiber holds.

Big save!

And Philipp Kohlschreiber takes some confidence from it, lovely net play to bring up the advantage in his favour.

Martina Navratilova
Nine-time Wimbledon singles champion on BBC TV

Halep just doesn't want to move forward and on grass that will bite you...eventually.

She had a bit of an escape there. Sasnovich is picking up her game.

Philipp Kohlschreiber can't deal with a wide Novak Djokovic return as he palms it into the tramlines.

Set point Djokovic.

Two break points but Aliaksandra Sasnovich fails to punish Halep for her errors from the back. The Romanian is serving well but she isn't, so far, willing to come to the net to attack her opponent.

She holds, but it's getting tougher for the former French Open champion.

Image source, Reuters

Third seed Karolina Pliskova is a set and a break up on Court 2 against Lin Zhu of China.

And seventh seed Simona Halep, a quarter-finalist here in 2016 and 2017, is a break up against Aliaksandra Sasnovich on Court 1.

A shock is still brewing on Court 3, though. Aryna Sabalenka has just lost the first set 6-2.

• Last year's men's runner-up Kevin Anderson, who has had injury problems this season, eased past Andy Murray's doubles partner Pierre-Hugues Herbert of 6-3 6-4 6-2.
• Heather Watson was the first Briton through to the second round with a 7-6 (7-3) 6-2 win over American teenager Caty McNally.
• Stan Wawrinka powered past Belgian qualifier Ruben Bemelmans 6-3 6-2 6-2.
• Eighth seed Elina Svitolina outclassed Australia's Daria Gavrilova 7-5 6-0.

Novak Djokovic is slowly warming up in the SW19 sun, he's pinging everything back with interest and the Serb engineers his way to 0-30.

Doesn't get his first challenge of that tournament right, mind. That Kohlschreiber was right on the money and the German fights back to level - 30-30.

Image source, Getty Images

Boris Becker
Three-time Wimbledon champion on BBC TV

I really want the young guns to show up this year. I don't buy that they're 'too young'.

It comes down to a question of mentality. Age is just a number - and that works at both ends of the scale.

Not the start Philipp Kohlschreiber needed when serving to stay in the set, a double fault.

There was no questioning Novak Djokovic's billing as the top seed in the men's draw, but some people - cough, Rafael Nadal - were unhappy about the placings this year.

Nadal, the world number two, has been handed the third seed, below Roger Federer, the world number three - and the Spaniard is not too pleased.

But chief executive Richard Lewis says it's not controversial.

"There's always going to be disappointed players. It's a formula, it's not discretionary. It's been in place for a long time," he added.

"From our point of view, it wasn't controversial because we had no choice. I think there's a good logic to the formula, it reflects grass-court play, and that's where it is for this year.

"You could take the view that grass is so good now that the surface is not such a big factor but, when you look at the statistics, there are some players who perform better on grass consistently, or relatively consistently, compared to others so I think there's a pretty strong case for it."