Root defends the next three balls from Cummins before a straight drive is cut off, preventing him from reaching his fifty.

Last ball of the over - it's back of a length and Root can only fend it into the leg side and he stays on 49.

Alastair Cook prods into the covers for a single and that's the hundred partnership for him and Joe Root.

Terrific stuff from England's most experienced pair. Cook onto 92 and Root unbeaten on 49.

Andrew Samson
BBC Test Match Special statistician

It is 35 Ashes innings without a hundred for Alastair Cook since his last in 2011.

Lyon drops short to Root, who shifts back and short-arm swivels it backward of square for four.

A better length from Lyon in response sees Root back and showing the maker's name for the rest of the over.

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Despite his stomach ailment, Cummins continues to charge in gamely, sending down a decent yorker that Cook does well to keep out.

Cook defends a couple before yet another sumptuous punch down the ground. Warner scampers after it but the ball wins the race, the Aussie opener unable to gather as it runs over the ropes.

That's Cook into the 90s. Around 15 minutes until close of play.

Michael Vaughan
Ex-England captain on BBC Test Match Special

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Mitchell Starc is a massive loss for Australia. He creates the extra pace and the different angles.

This looks like an attack that you should be able to prepare for but when you have Starc you know there will be the odd delivery that you can't prepare for.

Lyon continues to wheel away, Cook calmly repelling it until he edges low towards slip.

Crucially it falls short of Smith, ricocheting away to let Cook pick up a single.

Root goes back and works it away through mid-wicket for a couple.

Michael Vaughan
Ex-England captain on BBC Test Match Special

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It has been a remarkable day for England. This pair have played with such control. They have to see their team through to stumps.

I don't think I have seen Alastair Cook hit so many shots down the ground. It shows you this pitch may be starting to play better.

England are over halfway to Australia's total for the loss of only two wickets. Handy.

Can they keep accumulating even as the pitch slows? That helps, Cummins straying too short and straight, with Root easily swivelling it round the corner for four.

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Thanks Matt, no pressure eh?

Nathan Lyon to Alastair Cook, who takes off for the quickest single I think I've ever seen him run. Good thing he sprinted that too - the throw whistling past the stumps as Cook slid the bat in.

Joe Root sweeps at a full one, it's off the bottom edge, through his legs and away for four. Streaky. Without that thin edge he'd have been plumb lbw. That ball was too full for a sweep.

The England captain clips one away for a single.

Moving to 260-3, Australia were on top - only for skipper Steve Smith to chop a short, wide one from Tom Curran onto his stumps for 76.

That sparked a collapse for the hosts. Mitchell Marsh dragged on from Chris Woakes, while a resurgent Stuart Broad removed Shaun Marsh lbw for 61, before James Anderson and Broad blitzed away the tail, making use of reverse swing and a pitch keeping low.

Australia all out for 327 just after lunch and England have gone about their reply in fine style. Alastair Cook has looked back to near his best, save for being dropped by Smith on 66, while Joe Root is also finding some form.

Mark Stoneman offered a leading edge to Nathan Lyon, who took a superb return catch above his head, while James Vince was lbw to Josh Hazlewood and failed to review, with replays suggesting he might have got an inside edge. The hosts are weakened by Pat Cummins battling a stomach upset, which is limiting his overs and his speed.

Alastair Cook moves into the 80s. Any sign of nerves? Doesn't look like it yet. A nudge through the leg side and now a lovely drive through the covers. There is frustration that it has taken until the Ashes were gone but you can't understate how good an innings this has been from Cook.

I'm starting to get excited about the prospect of a century and so are the England fans. They're increasing the volume in the stands.

And with that commentator's curse perfectly set up it's time for me to hand over to Jack Skelton who will take you through the close. It has been a great day for England, don't mess it up, Jack.

Two more to Root brings up the England 150. England's most experienced duo are 30 minutes or so away from confirming this as England's best day of the series.

Anyone want to predict the conversations going on here between the main men on either side?

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If you're just waking up there was a little spell half an hour ago when Australia really threatened Alastair Cook. Steve Smith put a catch down off Mitchell Marsh and there was an lbw turned down but now Cook is taking full advantage of that reprieve.

A rare wide delivery from Hazlewood and Cook cracks the ball between point and gully for four. When do we start to mention the 'H word'?

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Another over of Nathan Lyon off spin without the ball really spinning. Maybe everyone criticising Moeen Ali in the first innings was being a little hasty.

A couple of singles from the over take this partnership to 64.

Edward Palarto: I find it even more irritating that England decide to turn up when there's nothing to play for. Is that just me?

I'm publishing that bold statement from Swanny but if England collapse he is solely responsible.

The ever-dangerous Hazlewood keeps going in this impressive spell. He has bowled a lot of good balls and for a second it is a heart in mouth moment as Joe Root almost gets a feather on a pull shot through to Tim Paine. Hazlewood appeals tentatively but there is nothing from anyone else.

Root survives and adds a couple more to the total elsewhere in the over.

Graeme Swann
Ex-England spinner on BBC Test Match Special

I think England will get a lead. A couple of big centuries from these two and the likes of Malan and Bairstow will follow it up. I think England will win.

But whichever team wins they are going to have to grind it out as the pitch is only going to get slower.

Image source, Reuters

A change of angle for Nathan Lyon. He goes round the wicket to Joe Root but after a few dot balls Root is able to tick over with a single into the off side. With the ball not spinning, Starc not playing and Pat Cummins struggling with illness, this is a really good opportunity for these two.