The only regret for the ex-Everton man is that he did not go home with the match ball – as the Hammers could easily have been on the wrong end of a hammering.
Right from the start, United had the kind of pace and power that has been missing for so long at Old Trafford. Yet For all their dominance United had failed to make Joe Hart work as much as they would have hoped.
The on loan City keeper was given plenty of stick from the Stretford End – and that was before he was picking the ball out of his net.
The opener came just after the half hour – with another new signing Nemanja Matic making a crucial tackle to win the ball back. Marcus Rashford ran at pace towards the visiting defence and slipped it through to Lukaku whose shot beat Hart and went in off the post.
Phil Jones pays close attention to Javier Hernandez who had little chance to shine on his debut.
Edimlson Fernandez got his shot away on the edge of the box and it flicked off Eric Bailly before stinging the palms of David de Gea. It was a fully deserved half-time lead for United and Rashford fluffed a chance to make the points safe soon after the re-start.
However the home crowd did not have to wait long for a second as Mkhitaryan floated over a free-kick and Lukaku got his head in to score.
Again the Hammers could have hit back as Marko Arnautovic’s looping header bounced on the top of the bar. But United were looking like scoring too and a well worked move saw ex-City defender Pablo Zabaleta deny Lukaku a hat-trick with a superb block.
And Rashford cut in from the left and unleashed a brilliant right-footed shot which hit the base of Hart’s post.
Anthony Martial came off the bench to score the third for United. It was only a matter of time though before United found their way through the Hammers back line again, and this time sub Anthony Martial was able to roll the ball into the far corner for the third on 88 minutes.
There was still time for a fourth, which United thoroughly deserved, when Paul Pogba curled a 20-yard effort low into the bottom corner. Paul Pogba added the fourth goal with his curling shot from just outside the area