You can't move anywhere Matthew. And if there are no entries here for five minutes then you know where I've gone...

No toilet breaks needed for Tsitsipas or Thiem. The Austrian to kick off the second set...

Matthew Henry
BBC Sport at the O2 Arena

Plenty of people rush for the exits from the arena after that first set. It was a long one - lasting over an hour. Refreshments and toilet breaks are needed. There's still a lot of tennis left in this.

To illustrate how close that set was, we see the stat about total points won. Thiem has won 45 of them, Tsitsipas 44....

Got it! Thiem takes a moment to choose his weapon and then whacks his favoured ball down the middle. Tsitsipas sticks some strings on it but is it not enough.

Thiem ahead!

Image source, EPA

Ah, spoke too soon. A poor second serve is punished by Thiem and the Austrian has a second set point. On his serve...

How are your nerves Stefanos? If they're like his dad Apostolos's - he's casually swigging water - then he'll be fine. A volley is put away and we're all square...

Thiem lands the first serve but then is a little over-zealous with a forehand down the line. Thiem peers around the line to will it in... it's out. Back on serve.

But an ace steadies the ship and gives him a set point...

A mountain to climb for Tsitsipas. Holding serve is all he can do. A Thiem error is followed by a body serve which shakes the Austrian.

Two serves for Thiem. Two points for the first set...

Matthew Henry
BBC Sport at the O2 Arena

Eh? Has the crowd changed its mind? "Dom-in-ic" is the chant now. Maybe they're just backing whoever is on top.

Back to business... a Thiem first serve goes out wide and Tsitsipas' return is well wide. The Greek checks the technology... out.

Thiem lands a first serve which Tsitsipas can only smack long. Time for a swig of water and a moment of reflection...

Tsitsipas is on the board with a backhand winner and moves within one when Thiem hits into the net from the back of the court. Questions asked.

Strong second serve from Thiem, Tsitsipas goes into the net.

And then the Austrian goes forward and bats away a volley for a 3-0 lead.

Boris Becker
Three-time Wimbledon champion on BBC TV

Usually the guy who is more proactive wins the tie-break, the one who wants to make things happen.

Tsitsipas wants to check a return which is called out. Is it out? Yes. Mini-break to Thiem.

Image source, EPA

Thiem's racquet has turned into a spade - he's dug himself out of a hole. The Austrian holds and that means we're getting a one-way ticket to Tiebreak Town.

Tim Henman
Former British number one on BBC Two

It seems like both players play their best when they are behind in the count. When they are behind they have found the big first serves and dominated the baseline rallies.

Suddenly Thiem realises he could be in a spot of bother if he doesn't pull his finger out. That's what his team - led by coach Nicolas Massu - are telling him too as they rise to their feet.

The Austrian ups the ante and starts to find his range with his forehand, pushing Tsitsipas back and swinging the game back in his favour for 40-30.

Tsitsipas comes forward again in a bid to nip this in the bud, Thiem's eyes light up as he sees a gap down the deuce side... but puts a backhand long. Deuce!

For the second time in the match, Thiem is serving to stay in the set...

Initially it doesn't go to plan as a routine backhand crashes into the net and gives Tsitsipas a 0-30 lead.

Chair umpire Ali Nili put his fingers close together without touching a few moments ago, indicating how close a line call was. He could also have been gesturing how close this match is. Barely a cigarette paper between them.

That's illustrated when Thiem can't take advantage of a soft second serve by Tsitsipas at 30-30 and wallops it long. It's the fine margins folks.

Tsitsipas makes the most of that let-off to hold by landing a first serve down the middle and put the pressure back on Thiem.