Michael Vaughan
Ex-England captain on BBC Test Match Special

The Australians have bowled a couple of good bouncers to Stoneman and they should have a short leg in place. He hasn't played a pull shot all series.

You'd move gully five or six yards closer, get a short leg in and pepper him.

Cook made a double ton just six Test matches ago. He doesn't have a great record against Australia, granted, but I still think there are runs in him. Also, who replaces him? It's taken England almost four years to replace Andrew Strauss. Let us know your thoughts.

Image source, Getty Images

Alex Corps: As sad as it is to say it, following years of service and leadership, maybe Cook's time is running out. He needs a very good second innings if he's to challenge Border's record

Lewis Wadsworth: Cook needs dropping. Hasn't been playing well enough for a long time to be an opening batsman

Ian: Alastair Cook is in no form at all! He's been a great servant for England but 150 Tests have taken their toll. I think he will retire from Test cricket after these Ashes, he looks spent

Starc gives Stoneman a filthy look as he bangs in a bouncer and the batsman fends it loosely into the air. It lands in between two fielders yet again. Stoneman had absolutely no idea where that was heading, the ball really rising up into his grille and surprising him.

And what a response that is! Starc goes full, Stoneman expects it and he thuds the ball back past the bowler and into the boundary rope. James Vince also did exceptionally well there to jump up and let the ball pass by.

Eng 27-1published at 6.1 overs

6.1 overs

Ooh, Mark Stoneman's broken his bat! Starc goes short and Stoneman pushes forward, the ball gets high on the bat - and bends the handle in half! That hit very high up on the bat and the handle has bent like jelly. Out comes sub fielder Mason Crane, with six bats for Stoneman to choose from.

Image source, Reuters

Dan Norcross
BBC Test Match Special

This 'slow-paced' pitch has still got England's openers hopping about...

The first short ball of the match and dearie me, Josh Hazlewood gets some bounce on that. It gets big on Mark Stoneman, who thrusts his bat forward, and the ball cannons off the glove and up into the air. It goes over where short leg would be, were there one in, and drops in front of an advancing fielder. Stoneman, wisely, takes a single. Full goes Hazlewood, and James Vince jabs his bat down and defends.

Ben Walton: Cook has been absolutely gubbins this whole series, has to be changed.

Aarran Shaw: Oh no. Australia have removed Cook and now they’re into the tail.

The replay shows that that ball was indeed cannoning into Cook's stumps. I wonder if he read the length wrong. He'd moved very deep into his crease. It wasn't exactly slow from Starc, either, the ball coming down to Cook at 92mph. James Vince is the next man in and Starc instantly pushes the ball wide, encouraging him to drive.

Graeme Swann
Ex-England spinner on BBC Radio 5 live

This is worrying for England. It's a full ball, everyone knows Starc likes to bowl full and he just played all around it. Was he waiting for the ball to swing?

Cook's head fell over to the off side and that would have thudded into the stumps. It was as plumb as you can get.

Graeme Swann
Ex-England spinner on BBC Radio 5 live

It has been a very positive start from England, particularly from Mark Stoneman. This outfield makes the difference - you get full value for every stroke. It is rapid.

You don't even have to run, it's brilliant.

Alastair Cook is in on the act now, as a push through the covers off Josh Hazlewood goes flying down to the boundary. David Warner tears after it like Roadrunner, and ends up doing a cartwheel over the rope a few seconds after the ball. It's a quick outfield. Hazlewood goes full and Cook blocks, before the final ball of the over just nips past the outside edge of Cook's dangling bat.

Andrew Samson
BBC Test Match Special statistician

Image source, Getty Images

Alastair Cook is by some distance the youngest person to reach 150 Tests. Sachin Tendulkar was the youngest before today. Cook is 33 on Christmas Day.

He has played in 148 Tests in a row now, Allan Border has that record of 153 in a row.

It is beautiful in Perth. Bright blue sky, hazy sunshine. The spectators are soaking themselves in sun cream. Alastair Cook gets off the mark in his 150th Test with a single that's clipped off his pads,before Mark Stoneman is squared up by a lovely 90mph tempter from Starc.

That's slightly less good from Starc, going for the yorker and drifting down leg, and Stoneman gets a tickle on it to help it away for four. And again! Full and straight, too straight, from Starc, and Stoneman batters it off his toes for a boundary. And that'll be four to end the over too, as Starc drifts a touch wide, and Stoneman drives it through backward point. Just the 13 runs from that over...

Graeme Swann
Ex-England spinner on BBC Radio 5 live

Australia won't be afraid to pitch it up early on, they know the length to bowl. They want people driving.

Stephan Shemilt
BBC Sport in Perth

Welcome to the Waca. The name itself conjures a harshness, before you even think of the pitch, the burning sun and England's awful record here. The ground itself, though, has a ramshackle charm, so different to the efficiency of the rest of the stadiums in this country. Stands of different heights, grass banks, trees. It's lovely.

Here's Josh Hazlewood, and he raps Mark Stoneman on the pad almost straight away! There's movement for Hazlewood, the ball shaping back in to Stoneman as the bowler goes full, and it raps him low on the pad. That's sliding down leg, though, and umpire Erasmus shakes his head. Stoneman bunts a delivery up to mid-off, before he gets the first runs of the innings with a delightful drive for four. He timed the pants off that, the ball thudding off the middle of the bat.

Glenn McGrath
Ex-Australia pace bowler on BBC Test Match Special

Mitch Marsh gives Australia a lot of options. He fills the hole in the middle order, strikes the ball so well and offers a lot of bowling options on a flat pitch.

Him coming in allows Steve Smith to keep the three quicks fresh.

Many a fine essay has been written while listening to the cricket. It's how I got through university. Mitch Starc goes full to Alastair Cook, who stays in his crease and plonks his bat down. Starc's second ball comes down to Cook at 90mph, and Cook shuffles himself in line and defends. A maiden to begin with.