Play resumed at 14:45 BST before rain returned at 17:00 and no further play possible
Brook drops Marsh on 31 - tough chance at short leg
Labuschagne caught behind off Root for fine 111 - given on review
Australia lead five-match series 2-1 and will retain Ashes if England fail to win
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A big 'ohhhhh' from Jonny Bairstow - but that could just be because it's amplified by him being stood up close to the stump microphone - as the last ball of Chris Woakes' over hits Mitch Marsh on the pad.
Woakes, who can see it was slipping down leg, also blows his cheeks.
Phil Tufnell
Former England spinner on BBC Test Match Special
Marsh and Labuschagne have looked very composed so far.
Mitch Marsh stands at the crease with a wide stance, his barrel chest stuck out relishing the contest.
England wicketkeeper Jonny Bairstow has decided to stand up at the stumps to Chris Woakes to counteract Marsh's determination to come down the track.
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Is it bad that my wife is in labour but I'm more excited that England are out bowling?
Iain
Between overs there jeers, boos and some chanting as Marnus Labuschagne receives treatment on the hand which clocked a blow from Mark Wood in the previous over.
Andy Zaltzman
Cricket statistician on Test Match Special
Mark Wood yesterday became the 50th England bowler to reach 100 Test wickets. He's currently at 101 wickets. He's dismissed Steve Smith twice in this game for just nine runs.
Only one England bowler has ever had a better match against Steve Smith, getting him out twice for fewer runs, and that's Test Match Special's very own Steven Finn. He got him out just twice for seven runs at Edgbaston in 2015.
Jim Maxwell
BBC Test Match Special
A very good half-century for Marnus Labuschagne in this Test, it hasn't happened in this series quite yet but this might be where he gets into a lengthy partnership.
A trademark flick off a full ball from Mark Wood's fourth ball of the over brings Marnus Labuschagne a couple of runs and his 16th Test half-century.
Matthew Henry
BBC Sport at Old Trafford
Marnus Labuschagne has taken his place at the non-striker's end on the wrong side of the stumps twice now. A cynic would say he's doing it on purpose to waste time.
Mark Wood bounces Marnus Labuschagne with the first ball of his next over and the Aussie batter attempts to turn it round the corner, but instead gloves a pull shot and is left shaking his hand in pain immediately afterwards.
Jim Maxwell
BBC Test Match Special
It's good to see Australia getting on with it.
Jonathan Agnew
BBC cricket correspondent on Test Match Special
What an extraordinary shot that was! It was like something out of the IPL.
Chris Woakes is a fraction short and wide, and Mitch Marsh comes forward to it in a positive fashion and thrashes it through backward point.
Next ball, Marsh plays a bottom-handed hoick across the line towards cow corner. Moeen Ali sprints round, spotting a glimmer of a catching opportunity, but the ball thuds into the turf before dribbling to the boundary sponge.
Back-to-back boundaries for the Aussie all-rounder.
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What happens results wise if the test ends early due to the weather? Is the result just as the score stands at the time?
Max
It will finish as a draw Max. That would mean Australia are 2-1 up in the series still and will retain the Ashes. England would only be able to draw the series 2-2 with one Test remaining at The Oval from Thursday.
Just the one over from James Anderson as he is replaced by Chris Woakes, who was off the field towards the end of play last night so had to wait 11 minutes before he could bowl today.
Woakes' first ball is eased square by Marnus Labuschagne for a single.
Phil Tufnell
Former England spinner on BBC Test Match Special
You just have to keep calm now if you're the England bowlers. If you get overly excited you start to lose your line and lengths.
#bbccricket
Matt Teague: My adrenaline is sky high right now! I can’t keep still.
Stuart Broad, wearing a wide-brimmed sunhat despite the absence of any sun, sprinkles a handful of sawdust down into where Mark Wood is landing his front foot on the crease.
Wood's penultimate delivery is right on the toes of Marnus Labuschagne who works it neatly for a single into the leg side. Mitch Marsh blocks the final ball and offers a guttural 'no' to his batting partner at the non-striker's end.
It feels tense.
Jonathan Agnew
BBC cricket correspondent on Test Match Special
There was a little inside nick I think.
It's gloomy, and the lights are on, as Mark Wood cuts a striking figure as he bounds into the crease with the kind of enthusiasm you would expect from him in this situation.
His third ball shapes into Marnus Labuschagne and hits him on the back leg, prompting excited 'ohhhhh' from the England slip cordon. However, there looked to be some bat on that.