Jonathan Jurejko
BBC Sport at Eastbourne

After an understandably rusty start, Williams is starting to find her rhythm more. Her ball-striking is cleaner and crisper in this second set.

In other news, the setting summer sun is being blocked by some clouds. Feels a little dark on court.

But it is the longest day of the year, of course, so there is plenty of light left for the deciding match tie-break.

How about that!

A sublime cross-court backhand from Williams brings up set point - and she wasn't going to let that pass her by.

We head to a final-set tie-break to decide who will progress from this one.

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Efficient work on serve initially by Williams takes her to 30-0. Two points to go.

Jabeur nets, though, and the Tunisian then takes a nasty slide as she reaches for a shot at the net. A painful one, but she's back up and ready to go again.

That'll do nicely! Serena Williams arrows a forehand down the line and there's too much on it for Marie Bouzkova.

The American will serve for the set.

Image source, Getty Images

A booming return from Serena Williams forces Sorribes Tormo into the net.

The American is certainly growing into this contest.

Superb! Williams brings Sorribes Tormo in and then executes a delightful lob. Three break points...

A ferocious volley from Serena Williams seals what feels like the first hold of serve in a long, long time. Five games, in fact.

It's heating up nicely on Eastbourne's centre court!

Ouch! Serena Williams drives a volley at the net which whacks Sara Sorribes Tormo in the leg. An immediate apology comes from the American.

Ons Jabeur's face tells us even she felt that one. 30-0.

Another break!

Serena Williams takes charge of the point, eventually landing an angled winner at the net to restore parity once again in the set.

Ons Jabeur follows up a big cross-court forehand from Serena Williams, sticking away a volley for 15-30.

Williams takes a tumble on the next point as she stoops down to try and meet the ball, but thankfully she's quickly back on her feet.

Serena Williams miscues with an attempted backhand volley at the net.

'Come on Serena' is the message of encouragement shouted from a member of the crowd.

Serena Williams and Ons Jabeur see their good work immediately undone as Sara Sorribes Tormo and Marie Bouzkova break again.

That's a third successive break of serve in this much more even second set.

Sorribes Tormo moves like lightning at the net to punish a Serena Williams shot from the baseline.

Trailing 15-30, Williams brings out a whopping first serve to draw level, but they'll have to face a break point here...

Oh and it is a first break of serve for Serena Williams and Ons Jabeur!

We're straight back on serve in the second set.

Into the net from Sorribes Tormo. Two break points...

It's a long way back now for Serena William and Ons Jabeur.

The pair take the first point on Sara Sorribes Tormo's serve, but somehow they lose out in an entertaining net exchange. Can they create an opportunity from here?

Ons Jabeur lets out a cry as she slaps a forehand into the net to concede the break. There was just no way through!

Excellent stuff too from Sara Sorribes Tormo, who curves a forehand into the corner for 15-30. Another lob executed to perfection by Marie Bouzkova over Serena Williams. Two break points...

Superb hit! Marie Bouzkova nails a backhand down the line to seal the game, after Ons Jabeur had reduced the gap to 40-30.

Serena Williams is appearing in doubles competition on grass today for the first time since Wimbledon 2016, when she lifted the trophy along with her sister Venus.

Just the 14 Grand Slam women's doubles titles to go with her 23 singles wins.

A missed volley suggests she's still getting up to speed here, but Williams shrugs that off to respond with a powerful smash on the next point.

Lovely team-work. Jabeur pounces at the net after good work from Williams.

The American is then caught out by a wonderful lob from Bouzkova, but a neat first serve seals the hold.