Adam Yates
Former Vale defender on BBC Radio Stoke

It's so tense, it's such an anxious time.

Ellis Iandolo kicks the ball out from the goal line for a Port Vale throw-in to save it going out for a corner.

The incoming throw bounces around the penalty box a bit, but Swindon clear the threat as the clock ticks rapidly down.

The fourth official then signals for four minutes of added time.

Ged Scott
BBC Sport at Vale Park

From a once bouncing Burslem, it has gone eerily quiet here over the last 10 minutes or so as the tension bites. At both ends.

Vale winning a corner and then going so close from it released a little steam from the pressure cooker. But it still feels like something might blow before we’re forced to endure another half hour of drama!

Darrell Clarke has his head in his hands as Nathan Smith sends a header just wide for Port Vale.

Five minutes left for either side to find a winner or we're going to extra time...

Image source, PA Media

Oof that was almost a huge error from Port Vale.

Mal Benning goes to clear a Swindon cross into the box, and he ends up chesting it right at Aidan Stone who has to dive down to save it from running into his own net.

You sensed Stone wasn't quite expecting that!

A first change of the night for Swindon. Louie Barry is taken off by Ben Garner, with Ben Gladwin coming on with 10 minutes of normal time left.

Steve Hale
Ex-Swindon goalkeeping coach on BBC Radio Wiltshire

It's getting to that stage of the game when one mistake or one piece of quality could win it for them and knock us out. I'm getting a bit nervous.

This match is going end-to-end at the moment.

Neither side want to take this match to extra time if they can avoid it, by the look of it.

Another change for Port Vale. Kian Harratt is taken off with Ryan Edmondson coming on in his place.

What an opportunity for Port Vale who have the best chance of the half to go 2-0 up on the night.

Harry Charsley picks up a loose ball on the edge of the box and somehow picks out James Wilson in the box.

But Wilson's first shot is saved by Lewis Ward and then he fires the rebound over the bar. Golden chance.

Steve Hale
Ex-Swindon goalkeeping coach on BBC Radio Wiltshire

Swindon are starting to dominate the ball and Port Vale are playing on the counter-attack.

I did ask at the start of the game how long Port Vale could keep that intensity up for and perhaps the Vale legs are starting to tire.

And now Swindon's passing game is starting to come out perhaps that will make it even harder for them.

Swindon are knocking on the door of the Port Vale goal.

Jonny Williams does well in space and cuts inside towards the top of the Vale penalty area, but he doesn't quite connect with the ball properly and his effort goes wide of the left post.

Adam Yates
Former Vale defender on BBC Radio Stoke

Image source, Rex Features

That's the best chance of the game for Swindon.

Jack Payne makes a dangerous and darting run into the box and his shot gets deflected over the bar.

The Swindon number 10 then goes out to take the following corner and Mathieu Baudry volleys the ball on the turn from a few yards out, but it agonisingly flies over the bar.

Swindon are upping the pressure here.

Adam Yates
Former Vale defender on BBC Radio Stoke

There's plenty more drama to come in this game. Both sides know they have got about 25 minutes to get a result and if it goes to extra time there are going to be some tired legs on that pitch.

Ged Scott
BBC Sport at Vale Park

Image source, PA Media

Sometimes you can tell which way a football match is going. But not this one.

It’s lurching back and forth like a fairground swingboat.

And both sets of fans sound very loud, equally confident.

So hard to call, but it’s sure making for a cracking atmosphere.

Kian Harratt almost breaks the Swindon defence but the linesman flags the teenager offside.

Mal Benning then tries his luck with a shot from long-range but it goes over the bar.

We're just edging over an hour into this match and it's shaping up to be very finely tuned.

There's definitely a lot less between these two sides this side of the half-time break.

Darrell Clarke makes the first change of the night to his Port Vale side.

Jake Taylor makes way for Harry Charsley.

Steve Hale
Ex-Swindon goalkeeping coach on BBC Radio Wiltshire

It definitely feels better for Swindon. There has been more attacking intent but they're still to really test Aidan Stone in the Vale goal.

They still need to find that missing piece of the jigsaw,