But with the allotted four minutes of added time played, Scott McTominay conceded a penalty by swinging a high boot dangerously near Mohamed Elyounoussi's face.

But Onana, who has come in for criticism since his £47m summer move from Inter Milan, turned Jordan Larsson's effort wide with what turned out to be the very last action of the game.

The victory breathed new life into a Champions League campaign that had started with successive defeats for Erik ten Hag's side.

It was another night when United's overall performance would not stand up to much scrutiny but, as on Saturday, the manner of the victory was secondary to the eventual outcome given the enormous legacy of the man they were trying to honour.

"First half was not so good - a difficult game. They were well organised and it was difficult to create chances, we didn't get the right build-up so we didn't get the right tempo," said Erik ten Hag.

"The second half was better. First half pressing did not happen on many occasions, so second half both things were better and the build-up was better.

"There were more switches and we created more chances. The win was justified - but it was a narrow escape."

Maguire and Onana turn jeers to cheers

The two players that secured the precious win for the home side are men who have endured a torrid time recently.

Maguire would have been sold in the summer had he accepted the chance to link up with David Moyes at West Ham United, while many have questioned Ten Hag's wisdom in replacing David de Gea with Onana.

But when half-time substitute Christian Eriksen delivered a superb curling cross to the far post 18 minutes from time, Maguire met it perfectly, shrugging off the attentions of a defender to make sure he was in position to head home.

It was a moment to savour for the 30-year-old, who lost the United captaincy in the summer and at one point seemed to be Ten Hag's fifth-choice central defender, behind even left-back Luke Shaw.

The hosts should have eased their path to the final whistle with a second goal but after Alejandro Garnacho's initial effort was saved superbly by Kamil Grabara, McTominay sent the rebound inches wide of the post.

Skipper Bruno Fernandes also had a shot deflected wide in a pulsating finish but it seemed United would take the points anyway.

Instead, they had to rely on Onana to ensure victory was not stripped from their grasp.

The charismatic Cameroon goalkeeper's save will allow United to look ahead to the return meeting in Denmark two weeks from now knowing victory will almost certainly take them into second spot behind Bayern Munich in Group A.

Ten Hag's side still struggling for fluency

The header was Maguire's second goal in the Champions League

Repeated chants of 'One Bobby Charlton' and the volume of fans who gathered at the 'Holy Trinity' statue outside Old Trafford to look at the floral tributes underlined that while most had never seen him play, they are fully aware of the former United skipper's role in creating the modern-day United.

The problem at present is the current side is a shadow of what has gone before.

Ten Hag is trying to build something but there is none of the verve of the Ajax side he took to within seconds of reaching a Champions League final.

The first half really was poor and towards the end of the opening period came a passage of play that summed United's effort during those 45 minutes.

Having forced a throw-in in a promising position, United ended up playing the ball back to Onana as, evidently, there was no option offered going forward that invited a pass.

Onana took ages deciding what to do and despite having Raphael Varane and Maguire available for a short pass, he waved them away and attempted a long diagonal which sailed straight out of play.

The lack of options, poor execution and general lack of dynamism was far removed from the vibrancy of the great side Charlton played in and brought understandable boos from the home supporters at half-time.

Maguire's goal and Onana's save ensured a positive result, but this was by no means a convincing performance.