Exactly what Thiem wanted - a hold with the minimum of fuss. A 30-0 lead becomes 40-0 with the help of a net cord and, after a wild cross-court backhand gives Tsitsipas a foothold, Thiem stuns the ball with a iron-wristed volley at the net. That's the game.

Boris Becker
Three-time Wimbledon champion on BBC TV

Usually after 45 minutes you get a sense of who is ahead but I don't have that, I don't see who is dominating the rallies - it is really on edge.

Matthew Henry
BBC Sport at the O2 Arena

There was a tentative attempt to get a Tsitsipas chant going at that change of ends. It still needs work.

Dominic Thiem has already fended off three break points and the last thing he wants now is to face anymore in this game. That could prove terminal to his hopes of winning the first set. The Austrian serves to stay in the opener...

Thiem is sitting very deep behind the baseline which is allowing Tsitsipas to move into the net at will. That's been a very successful tactic for the Greek so far, doing the same to wrap up a fairly routine hold.

Boris Becker is urging Thiem to step in more. And who are we to argue with a six-time Grand Slam champion?

Image source, EPA

Matthew Henry
BBC Sport at the O2 Arena

A couple of Austrians have turned up with a big flag and have perched themselves just behind where Thiem was serving from in that game. It's fair to say they were delighted when he fought off the break points.

What can Thiem rustle up here? An ace is a promising start. One down, one to go.

Another hefty first serve leaves Tsitsipas scrambling, Thiem sensing his opportunity and springing forward like a greyhound after the lure.

A deep forehand is followed by a neat volley, allowing him to save both break points and then go on to hold.

Tsitsipas, as he does, sits motionless at the changeover and then decides when he gets to the baseline that he needs to change his racquet.

The new strings do the trick. Tsitsipas reads a Thiem serve out wide and returns it with interest down the line for 30-15.

Thiem doesn't land a first serve allowing Tsitsipas to dominate the baseline rally, then the Austrian fluffs his lines with a forehand into the net.

His reaction - an annoyed scream accompanied by a facepalm - tells us exactly what he thinks.

Two break points to Tsitsipas...

Image source, Reuters

Matthew Henry
BBC Sport at the O2 Arena

OK. The raucous cheer when that Hawk-Eye call ruled Tsitsipas' shot in confirms the crowd are backing the Greek.

He has saved more break points than anyone else this week - 86% of those he had faced before this match. Two more to the total now.

Tsitsipas saves that break point with a Borg-style gallop to the net - all legs, hair and a gorgeous volley to finish.

Soon the Greek has to dig out himself out of trouble again, another break point for Thiem, Tsitsipas getting another first serve thanks to the intervention of HawkEye.

Tsitsipas comes forward again and again it proves to be another fruitful mission, allowing him to stave off the second break point and go on to a vital hold.

Now then... a momentum shifter.

Thiem suddenly has a 0-30 lead but misses a half chance for 0-40 as he gets stuck a little deep.

The Austrian loops a backhand long in the next exchange - or has he? Yes, says HawkEye.

He's struggling with his eyesight, as is Tsitsipas judging by his Gary Lineker to Bobby Robson gesture to the court, when the Greek shanks a forehand wide.

Break point to Thiem...

A baseline scrap begins, only for Tsitsipas to hit long from the back of the court. Goes down as an unforced error. That's 30-30.

Thiem edges ahead when a shorter, punchy backswing from close to the baseline rocks Tsitsipas and the Austrian gallops forward to put away the volley for 40-30.

A hefty first serve burns the Greek's racquet and that's a good hold.

Image source, Getty Images

Oooh! This is a big miss. Dominic Thiem steps in and whacks away a forehand winner harder than he needs to. And it is wide! Thiem challenges but the human eye is proved correct by the electronic eye.

Big moment? Tsitsipas has a look at 15-30...

Crash! Bang! Wallop! Tsitsipas and Thiem go all Batman and Robin on us in a bruising rally which Tsitsipas comes out on top after 23 blows are traded. The Greek sticks away a drive volley for 30-0 - his seventh winner of the match already - then hits a service winner down the middle.

Brief respite for Thiem at 40-15 but any hope is quickly extinguished with a crunching forehand from the Greek which licks the line.

Matthew Henry
BBC Sport at the O2 Arena

Thiem's box were all up out of their seats in unison after their man saved that break point.

It was early but that could be important.

"A proper response," says Andrew Castle. Indeed it is. A brutal blow with that forehand leaves Tsitsipas struggling... deuce. And two more hefty strikes with his serve get Thiem off the hook.

Image source, AFP

Thiem brushes off those nerves, momentarily, at least as he battles back to 30-30. But then Tsitsipas earns the first break point of the match when he charges forward and scares Thiem into lob which drops a few feet away from Row A...

Boris Becker
Three-time Wimbledon champion on BBC TV

A little nervous beginning by Thiem, I sense. Maybe the occasion is getting to him slightly.

Oh hello. A half chance here for Stefanos Tsitsipas. A nervy backhand is clubbed long by Thiem for 0-15 and then he puts a volley past the baseline for 0-30...

History will be made with another first-time champion, continuing a remarkable run at the season-ending final...