Arsenal walk off triumphant, having won at Old Trafford for the first time in 11 attempts at Old Trafford. They’re into the semi-finals of the FA Cup - the draw is being covered live here - and I think they deserved this victory. They defended pretty well for the most part, scored a fine goal in the first half and were the better side after the break. The winner was a gift, but something like that always felt liable to happen and Danny Welbeck won’t care? He won’t. He was rewarded for his persistence and has dumped his old side out of the FA Cup. There will be more awkward questions for Louis van Gaal to answer after this, especially about Angel Di Maria’s conduct. “They’re not a good team,” says Alan Shearer on the BBC. He’s talking about Manchester United. Is he wrong?

90 min+5: Phil Jones pumps a long ball to No One and straight out for an Arsenal goal-kick. Oh dear.

90 min+4: This should be this. Mesut Ozil is released in the Arsenal area but elects not to shoot, setting up Sanchez instead. He takes the ball wide but still manages to shoot. De Gea somehow tips it wide. He is so good.

90 min+3: As soon as I say that, there’s mild panic in the Arsenal area as the ball is allowed to bounce - but Koscielny hacks it away.

90 min+2: Arsenal are looking solid.

90 min: Ramsey pierces the United defence with a pass through to Sanchez on the left, but De Gea steams out of his area to boot the ball away. There will be five minutes of Louis Time.

88 min: Sanchez and Ozil combine to set up Cazorla on the edge of the area, but his shot is scuffed and United attack down the left. Ramsey takes one for the the team and ends Young’s charge with a cynical foul. Yellow card.

86 min: Now Adnan Januzaj is booked for diving! He stormed past Monreal and into the area, but there was hardly any contact and he waited an age before his legs gave way. United need to practise their diving.

83 min: Angel Di Maria’s red card was monumentally thick, but was it as bad as this effort against Deportivo in 2013?

82 min: “Funnily, and despite the likelihood that they are going to lose tonight, this has been one of the more convincing recent performances by United,” says David Wall. “Not that that will be much consolation. But whatever effect the result might have for the league run-in, surely the most important thing for them in that respect is De Gea not bringing down Welbeck when he was through on goal to score. If he were to get a suspension then they’d have no chance of Champions’ League qualification.”

Has it, though? I think they were quite good in the first half, but they’ve been poor since the break. Arsenal have been the better side in the second half and United’s defence does not convince, while they’re never going to get where they want to go as long as Fellaini is in the side.

81 min: Rooney can fancy it all he wants, but his effort sails over the bar.

80 min: United have a free-kick on the edge of the area, Monreal handling a pass from Jones. Rooney fancies this.

77 min: “Whoa!” said Michael Oliver as Di Maria tugged his shirt. I suppose shirt-pulling is a bookable offence by the letter of the law. This won’t be the last you hear of this incident. “Good on Welbeck,” says Matt Dony. “Be happy you scored a goal for the team that pay you lots of money. I get why, say, Lampard might be restrained when scoring against Chelsea, but are any United fans upset at Welbeck for celebrating? Honestly? On Saturday, would any Spurs fans have cared had Sandro celebrated his goal?”

74 min: Loud boos float around Old Trafford as Danny Welbeck walks off and Olivier Giroud comes on. Giroud is involved immediately, turning a pass round the corner to Ramsey on the left. He cuts the ball back into the middle and there’s Sanchez in the middle. Who else would Arsenal want there? Sanchez hammers a volley towards the bottom-right corner, but De Gea denies him with a wonderful save! That was almost the game wrapped up for Arsenal.

73 min: Manchester United make their final change, Adnan Januzaj on for Marcos Rojo, who was apparently lucky not to get a second yellow card for an earlier tackle. Januzaj’s introduction means that we won’t be seeing Radamel Falcao this evening.

72 min: Alexis Sanchez produces a silky touch to pluck a pass out of the sky, before ghosting past Valencia, who pushes himself just outside the area. It looks too far to the left to shoot, but that doesn’t put Cazorla off. It’s straight at De Gea, though.

70 min: United looked better when Ander Herrera was on.

69 min: “Attack! Attack! Attack!” goes the chant from the United fans.

68 min: Young twists and turns on the left and lofts a cross to the far post. Fellaini is under pressure from Monreal and heads straight at Szczesny.

66 min: This is a sensible move from Arsene Wenger, who protects Hector Bellerin by replacing him with Calum Chambers. Bellerin was one foul away from being sent off.

65 min: The ball reaches Di Maria on the left of the area. Bellerin steams across to challenge him, but at the expense of a corner on the left. Di Maria sends it low to the near post, Carrick flicks it on and Smalling somehow diverts it over the bar from close range! What a let-off for Arsenal.

64 min: Marcos Rojo is booked for an ugly challenge on Santi Cazorla a couple of minutes ago, but the reason for the stoppage in play is a foul on Young by Bellerin, who’s already on a yellow card. Michael Oliver is lenient with the Arsenal youngster and lets him off.

62 min: Outrageously there was no muted celebration from Danny Welbeck. Who does he think he is?

61 min: Saying that, this effort from Di Maria is the closest either side have come to scoring a second goal in this second half. He volleys just wide from 18 yards after a good pass from Fellaini.

60 min: Ashley Young hauls Welbeck down on the left. It’s one of the more obvious yellow cards you’ll ever see. Arsenal are on top at the moment, with Michael Carrick struggling to adjust to the pace of the game in midfield for United.

58 min: Marouane Fellaini concedes two fouls in the space of about 10 seconds. He’s booked. Arsenal are starting to rule the midfield areas.

56 min: This has been a decent little spell for Arsenal, but overall the second half has been disappointingly scrappy. Still, there’s time for it to improve.

53 min: An appalling touch from Smalling presents the ball to Cazorla and suddenly United are exposed. He shifts the ball to Sanchez on the edge of the area, but Valencia takes the sting out of his shot from 18 yards and De Gea is able to make the save. United make problems for themselves at times.

51 min: Hang on, Aaron Ramsey has replaced Alex Oxlade-Chamberlain and Theo Walcott is back on the bench. Moments later, Arsenal are on the back foot, Di Maria hurtling towards the area and trying to release it to Rooney, only to go down under a challenge from Monreal. That was probably a foul, but nothing is given.

50 min: Oxlade-Chamberlain is down and the Arsenal physio is on. Theo Walcott will replace him. Aaron Ramsey is also getting ready.

49 min: Rojo wins a 50-50 with Oxlade-Chamberlain, who immediately pulls up. That might be a hamstring injury, but the attack continues, Rojo sending a cross to the far post. Rooney heads wide.

47 min: A low-key start to the second half. “If there was a hot green lady in goal, BGH would certainly score,” grins Mak Imamovic, the saucy blighter.

46 min: Phil Jones and Michael Carrick have replaced Luke Shaw and Ander Herrera and the second half can begin. There’s no word about any injuries. “A Fellaini-Carroll front two?” says Peter Oh. “Slot Rory Delap in behind them and watch the titles pour in.”

It seems that Michael Carrick and Phil Jones are going to come on for United.

“When you say that you’d love to see a front two of Fellaini and Carroll, is that like when people claim they’d love to see Farage as PM?” says Matt Dony. “Sure, it would be entertaining at first in a ‘can’t look away’ kind of way, but then the horrible reality would start to set in. Beyond (very) brief novelty value, neither option is a life I want to live.”

I want to see it. They should also be joined by The Big Giant Head from Third Rock From The Sun.

Roy Keane was unimpressed with United’s defending for Arsenal’s goal. ”It’s about tackling people,” he seethes. “Absolutely shocking, disgraceful.”

45 min: A long clearance from Shaw has Rooney on the chase. Szczesny comes racing out of his area and dispatches a nervy blast straight to Fellaini, who momentarily thinks about sending the ball straight back into the empty net from 40 yards, before remembering that he’s esentially an anthropomorphic tree. Di Maria and Herrera both pass up opportunities to shoot and eventually it goes back to Fellaini, who has a dig from 20 yards - it’s closer - which flies straight at Szczesny.

44 min: A free-kick to Arsenal, 30 yards from goal. Cazorla goes for goal, curling it towards the bottom-right corner with his right foot, but De Gea saves with ease.

43 min: Paul Scholes Marouane Fellaini pings a pass out to David Beckham Antonio Valencia on the right. Beckham Valencia wafts a lovely ball over the top to the scampering Ryan Giggs Angel Di Maria, whose low right-footer from a tight angle is saved by Szczesny. Rooney follows up with a chip on the edge of the area, but it’s a comfortable save for Szczesny.

41 min: This would have been an outstanding United goal. Fellaini stabs a pass down the left channel for Rooney, whose excellent first touch allows him to swerve away from Koscielny and knock a pass into the area to Di Maria. Unfortunately his first touch fails to match up to Rooney’s and Monreal is able to clear.

40 min: I’d love to see a front two of Marouane Fellaini and Andy Carroll.

37 min: Herrera picks up United’s first booking after Cazorla finds himself in the middle of a Herrera-Di Maria sandwich.

36 min: Young runs at Bellerin and moves down the outside, but the Arsenal full-back does well to block the cross behind for a corner on the left. Di Maria whips it in and Smalling heads a few yards over the bar. “Nice to read the game is livening up,” says Dan Hamilton. “You just know that in parts of Liverpool and North London, and probably all of Southampton and environs, there are fervent hopes for a proper blood and thunder encounter that ends in a draw. Followed by another blood and thunder replay that goes to pens.A couple of cards wouldn’t hurt either.”

35 min: The United fans are singing about this time that Patrick Vieira gave the ball to Ryan Giggs. I’m not sure what happened next.

33 min: Arsenal have to stop Di Maria getting the ball on to his left foot. Another delivery to the far post almost results in a horror moment for Szczesny, who spills the ball with his first attempt to catch it. Luckily he claims it at the second attempt, just before Fellaini can nick it away from him.

31 min: This cup tie sure has come alive! Bellerin reaches the byline on the right and lifts a cross into the six-yard box, where Welbeck’s downward forces De Gea to make a save low down to his left.

30 min: Arsenal can consider themselves hugely unfortunate not to have been awarded a penalty here. Ozil lobs a pass through to Welbeck, who goes down inside the area, Rojo all over him. Michael Oliver waves the appeals away, but the replays show that Rojo pulled him back. The only defence the Argentinian has is that the offence might have started outside the area. Other than that, he’s bang to rights.

27 min: Suddenly you can only hear the Arsenal fans. But...

23 min: Let’s just say that United are not entirely convincing when they’re playing the ball out from the back. A few errors are creeping into their passing, Blind in particular guilty of conceding possession in dangerous areas on more than one occasion.

22 min: This is better from Oxlade-Chamberlain, who goes on a power surge up the right flank, past one, past two, but not past Rojo, who brings him down unceremoniously. He escapes without a booking, however, and Ozil’s free-kick is cleared.

21 min: This is a waste from Oxlade-Chamberlain. The ball breaks kindly for Welbeck after a dust-ball of a scramble in the middle of United’s half. Welbeck finds Oxlade-Chamberlain in space on the right, but his chip into the middle is neither cross nor shot, the ball sailing harmlessly over De Gea’s goal.

20 min: Di Maria dribbles inside from the right, on to his left foot, and hangs a lovely pass over Mertesacker’s head and on to the adhesive chest of Marouane Fellaini. He brings the ball down at the far post but his lay-off to Young knocks the United winger off-balance and he skews his shot high and wide.

18 min: Cazorla chips a pass over the top to the onrushing Bellerin, whose volley clips Blind and flies wide. Goal-kick to Manchester United! “I’m not a fan of scrapping but Keane and Shearer would have been a great fight wouldn’t it?” says Paul Ewart. “One for the ages. I imagine a never ending Fast Show type affair with Keane as Begbie crossed with Joe Pesci to Shearer’s Black Knight crossed with Big Pete Bondurant.”

17 min: Arsenal are defending deep and in numbers, letting United have possession. They’re perfectly happy for Smalling to have the ball. His passing leaves much to be desired and Monreal has no problem cutting out a pass to Di Maria on the right.

16 min: Rooney loses the ball just inside Arsenal’s half, Ozil pinching his pocket, and Arsenal break. Cazorla finds himself running at the United defence for the first time, but his attempted pass through to Welbeck is poor and De Gea mops up. This game is in the balance.

13 min: The free-kick is better this time and Szczesny does well to come through the bodies and punch it away. But United continue to push. Arsenal can’t get out and Smalling - yes, really - pokes a pass through to Fellaini, who’s in the clear, one on one with Szczesny. The ball is perhaps just too far ahead of him to shoot, though, and Koscielny is covering, so Fellaini tries to turn and ends up fouling Mertesacker, almost on instinct.

12 min: Ashley Young is prominently involved. Coquelin taps him on the ankles on the left, conceding another free-kick. There has been some questionable defending from Arsenal already.

11 min: Herrera heads Cazorla’s corner away at the near post.

10 min: Sanchez plays an extremely clever slide-rule pass through to Welbeck, who peels away from his marker and wins a corner on the left.

9 min: United have dominated possession since that Sanchez chance.

7 min: Shaw pings a pass down the line, looking for Young. Mertesacker should cut it out, but instead he slips and diverts it behind for a needless corner on the left. Di Maria swings it to the near post and Rooney hooks it on acrobatically, but no United player can react quickly enough as the ball loops across the face of goal.

6 min: Arsenal have to defend this free-kick with 10 men, with Coquelin not allowed back on the pitch yet. They do so comfortably enough, Rooney’s flat delivery headed away.

5 min: Before the free-kick can be taken, Coquelin needs some treatment on a bloody nose. I think he was involved in a collision with Fellaini a minute or two ago.

4 min: This is going to be a long old evening for Hector Bellerin. Ashley Young skips past Bellerin on the left and the young full-back takes him out with a panicky challenge. He’s booked and United have a free-kick just outside the area on the left.

3 min: This is a highly promising start from Arsenal. The ball is sprayed out to Alexis Sanchez on the left, one on one with Antonio Valencia. Sanchez runs at a jittery Valencia, forcing him into the area, and shifts the ball on to his right foot. He aims a shot towards the far corner, but Smalling makes a vital block not too far from goal. Welbeck is sniffing around, hoping the ball drops his way, but De Gea plunges on it before the Arsenal striker can pounce.

2 min: United stroke the ball around at the back for a while. Then Rojo hoofs it 60 yards forward to Fellaini. A lot of money has been spent on this team.

We’re off! Arsenal, in their dark blue away kits, get the game underway, kicking from right to left in the first half, towards the Stretford End. “I assume the only reason you referred to Poor Jonny as ‘The Spitter’ is that ‘Not That Type of Player’ was too long,” parps Shaun Wilkinson.

And here come the players, striding out on to the Old Trafford pitch. The camera locates a chuckling Sir Alex Ferguson in the stands. He must miss the buzz of bein on the touchline on these nights. The atmosphere sounds great.

Here’s Louis van Gaal. He’s asked what sort of performance he wants. “That we beat Arsenal, because that’s the most important thing,” he says.

The BBC studio could be more interesting than what’s happening on the pitch tonight. It contains both Roy Keane and Alan Shearer.

“Rosicky is apparently ill (not injured, calm down Chris Meredith),” says Edward Chukwurah.

Yeah, calm down.

“Is there a typo in the team selection?” gasps Chris Meredith. “No Rosicky for Arsenal tonight? He hasn’t got injured again has he? He could be missed tonight.”

There is no typo. Rosicky is not in Arsenal’s 18.

How intriguing that Olivier Giroud has been left out for one of Arsenal’s biggest games of the season. Is it simply a case of squad rotation or is there something deeper to be read into Arsene Wenger’s decision? It’s less than two weeks since Giroud was hauled off against Monaco.

Tonight’s referee is Michael Oliver. Has a man ever been this happy to play an advantage before? It’s like he’s propelling the players with the power of his arms.