The television cut-aways to the ­enclosure housing the Arsenal ­supporters perfectly captured the anxiety. It was not supposed to be like this, not against this ­Manchester United. But the lesser spotted a­cceptable version of Erik ten Hag’s team was on show, fighting for the badge, and Arsenal were made to suffer.

Leandro Trossard scored their goal midway through the first half after a United defensive malfunction – of course it was – but the advantage was slender and everyone knew, most of all Mikel Arteta, that it could take only one moment to rub out.

Related: Manchester United 0-1 Arsenal: Premier League player ratings

With five minutes to go, there was thunder and lightning. Very, very frightening. Arsenal had not exactly made a habit of winning here in recent years, doing so only once in their previous 16 Premier League visits. They desperately needed the points, to answer Manchester City’s victory at Fulham on Saturday, to jump back above them at the top of the table, to make sure that their ­challenge would go to the final day next Sunday.

Arsenal got the job done, relief ­fusing with the euphoria when it was all over. The downpour at the very end was almost biblical, the ­hailstones pelting down too, the notorious Old Trafford roof getting a thorough examination and it ­certainly made for a vivid backdrop when Arteta and his players celebrated in front of the travelling fans.

Arsenal were well below their best in creative terms; their star players were defenders, namely Ben White and William Saliba. The result was the only thing that mattered. Does ­anyone think that City will slip up; they play their game in hand at ­Tottenham, of all places, on Tuesday night? City have never done so under Pep Guardiola when the title has been within their grasp. For Arsenal, it remains about believing.

Any pre-match optimism had been difficult to locate in United hearts and yet there was a ­tremendous roar from the home crowd upon the first ­whistle; excellent support ­throughout. It was surely in spite of the evidence contained on the team sheets. Call it blind faith, defiance. Or just backing your club.

Arsenal had been unchanged, ­bristling with assurance, ­momentum behind them. What remained so ­disorientating about United was the sheer number of absentees, ­especially at the back, where Casemiro ­continued alongside Jonny Evans in the wake of the horror show at Crystal Palace last Monday. There was no one else.

Arsenal were odds-on with some bookmakers to score at least three. Digest that, for a moment. Yet United appeared determined to show some personality and they might have scored first when Scott ­McTominay won the ball high up off Thomas Partey and, suddenly, ­Rasmus Højlund had a clear ­shooting chance. He slipped at the crucial moment.

United were good for the opening 20 minutes, winning a few duels, although Arsenal threatened on ­corners, Aaron Wan-Bissaka ­having to make one important clearing header. The problem, of course, is United’s near constant vulnerability, the sense that a structural breakdown is never far away.

It came when André Onana went long, Casemiro having shown for the short ball and White took a header from Saliba to feed it back up the inside right for Kai Havertz. The Arsenal centre-forward looked ­offside. That was until we looked along what passed for United’s line and saw Casemiro was still 10 yards back. Havertz ran around Evans to cross low. Trossard lost Wan-Bissaka to touch home.

Arsenal might have scored again on 29 minutes when White worked a give-and-go with the ­disappointing Bukayo Saka, burst away from Casemiro and lifted just off target. United, though, held their own up to the interval, despite struggling for clear-cut openings.

Ten Hag had recalled Sofyan ­Amrabat in midfield and he brought some muscle, earning a generous ovation when he was substituted late on. Amad Diallo, who started ahead of Antony on the right wing, showed twinkle toes and sharp turns. Kobbie Mainoo looked as if he could make something happen.

Arteta had won here previously as a manager, Arsenal’s lone league ­success of the recent past coming under him in November 2020 – the 1-0 pandemic ghost game that was ­settled by Pierre-Emerick ­Aubameyang’s penalty. Arteta needed his team to manage the game in the second-half. The longer it stayed at 1-0, the more his insides churned.

Declan Rice saw a shot blocked by Wan-Bissaka but with Diogo Dalot and Alejandro Garnacho driving variously up the left, the home crowd sensed an equaliser.

Garnacho was stopped in his tracks by one excellent Saliba tackle. On another occasion, the United winger dropped his shoulder to open up a shooting chance, stepping inside only to get the curler all wrong. ­Garnacho’s final action was too often a frustration.

• Download the Guardian app from the iOS App Store on iPhone or the Google Play store on Android by searching for 'The Guardian'.

• If you already have the Guardian app, make sure you’re on the most recent version.

• In the Guardian app, tap the Menu button at the bottom right, then go to Settings (the gear icon), then Notifications.

• Turn on sport notifications.

It was nervy for everyone ­connected to Arsenal. They sat deep at times, in the second-half, inviting United to make the game. Martin Ødegaard sent one shot too close to Onana but at the other end Antony – having come off the bench – pinched the ball ahead of Takehiro Tomiyasu before fluffing the shot.

Garnacho kept going, it kept on being nearly but not quite for him while Onana tipped over from the Arsenal substitute Gabriel Martinelli. The goalkeeper would also paw clear a Wan-Bissaka backwards flick and a drive from Rice.