Romelu Lukaku raises his arms aloft in front of the Old Trafford stands as Paul Pogba runs to celebrate with his new team-mate
Can he play you every week? For, let's face it, if Romelu Lukaku could, Manchester United would be racing certainties to win the league.
In his last 11 games against West Ham, this is the 10th match in which Lukaku has scored. A goalless draw for Everton at the London Stadium on April 22 was the exception, and there was no chance of it being repeated here.
Lukaku, and Manchester United, were in control from first to last and were not in the least flattered by the biggest win of the Premier League's opening round of fixtures. It would have been more had United taken more first-half chances, Marcus Rashford not hit a post and Joe Hart not made a couple of decent saves.
Lukaku fended off West Ham defender Winston Reid before smashing the ball past on-loan goalkeeper Joe Hart for the opener
Lukaku doubled his and Manchester United's tally after meeting Henrikh Mkhitaryan's free-kick with his head
Anthony Martial made the most of his late cameo after coming on for Marcus Rashford as he finished off a fine team move
Pogba sends Manchester United top of the table on goal difference with a fourth strike in the 90th minute of the game
ukaku celebrates with his new team-mate and close friend Pogba after the Frenchman adds a fourth and final goal
As for West Ham, this was a worrying start, despite the strength of the opposition. Slaven Bilic set out a team not to get beat and lost by four instead. Ennui or fatigue set in towards the end, too, allowing United to turn a convincing victory into an emphatic one.
True, West Ham were missing Michail Antonio and Cheikhou Kouyate, but that is no excuse. They are considered to have had a good summer and new striker Javier Hernandez even speculated whether he would celebrate if he scored against his old club. Maybe he should have set his sights a bit lower. Touching the ball for instance. Deep in the first-half, he'd still had fewer touches than either goalkeeper.
Lukaku must have been licking his lips in anticipation of this fixture, and so would his team-mates had they known how little resistance they would face. West Ham held firm for 20 minutes, then United started creating better chances, after 35 minutes they went ahead, after 53 the game was over and United's last two goals simply gave the scoreline a greater sense of realism. This was a genuine statement of intent from Mourinho's team, although they will need to be judged against opponents with greater resolve.
For much of the first-half we wondered why West Ham did not commit more men forward, then they did and it all became clear. In quick succession, West Ham won free-kicks inside the Manchester United half. On both occasions, they sent men up in numbers that had not ventured far before.
The first free-kick, taken by Marko Arnautovic was cut out by Manchester United's defensive line, setting up a quick counter-attack. From the second kick, West Ham were sloppy again, and Manchester United scored.
Lukaku uses the side of his left foot to guide the ball past Hart and his effort needed a deflection off the post to find the net
Lukaku turns towards his team-mates in celebration as the ball nestles in the back of the West Ham net in the first half
West Ham goalkeeper Hart stands still as he watches the ball bounce into the net after Lukaku guided it with his head
Hart screams in frustration as he sees his defence leave Lukaku unmarked and free to score Manchester United's second goal
Martial is congratulated by his Manchester United and France national team-mate Pogba after scoring United's third goal
Pogba dances in front of a jubilant Old Trafford crowd after capping a fine afternoon with Manchester United's fourth goal
Pedro Obiang was at fault. Receiving the ball and dawdling, his pass was charged down by the outstanding Nemanja Matic. From there, United were away. With Pablo Zabaleta well advanced there was huge space on the left and United exploited it perfectly.
Rashford sprinted upfield, making the yards and releasing Lukaku ahead at perfectly the right time, Matic helping with a magnificent decoy run. Lukaku had only Hart to beat and finished with impressive power in front of the Stretford End, the ball cannoning off the inside of the near post, England's goalkeeper helpless.
It had been coming. Manchester United were in control even if this did not convert to a wealth of goalmouth opportunity. The first real chance came after 20 minutes, a quick free-kick taken by Daley Blind to Henrik Mkhitaryan, who put Juan Mata in with Hart pulled out to his right to repel.
He did his best but Mata got the ball into the middle where Angelo Ogbonna led a deputation of three West Ham defenders smothering Lukaku. There were appeals for a penalty, rightly dismissed by referee Martin Atkinson.
In the 28th minute, a lovely ball from Paul Pogba found Mata but his unselfish decision to try to play Lukaku in again allowed Ogbonna to recover and clear just in time. Might it be the same old story for Mourinho's United – all the possession, not enough goals?
Not with West Ham to relieve the tension. Zabaleta made a cynical challenge on Rashford and was booked, Lukaku delivered further punishment from the free-kick. The excellent Mkhitaryan whipped it in from the left and Lukaku rose, inexplicably unguarded, to head the ball past Hart.
It won't convince those who claim Lukaku only punishes the meek – although he did score against Real Madrid last week – but it was just the start a £75m acquisition needs in front of his own fans.
West Ham's Edimilson Fernandes forces David de Gea into a fine save with the final kick of the first half at Old Trafford
Mkhitaryan believes he has made it 3-0 after scoring but sees his effort ruled out as assister Rashford was offside
West Ham summer signing Marko Arnautovic reacts in disdain after seeing his effort deflected onto the bar by De Gea
Rashford comes within inches of making it 3-0 as his fierce effort bounces off of the post and out of Hart's goalmouth
Matic tries a shot from outside the West Ham penalty box with Mark Noble and Pablo Zabaleta there to try and block it
Even better is the understanding Lukaku seems to have quickly developed with Rashford. When the young man was substituted with 11 minutes to go, he received an affectionate pat on the cheek from his partner, and the pair ran West Ham silly for much of the match. The locals will remember the last great nine and 19 pairing at Old Trafford: Andy Cole and Dwight Yorke.
Not that Rashford's withdrawal made any difference. On came Anthony Martial and, within minutes, he scored United's third, finishing sweetly, set up by Mkhitaryan once more.
Rashford was desperately unlucky not to get on the scoresheet, too, cutting inside and striking the post with a shot after 66 minutes. Mkhitaryan, Lukaku and Blind all went close in the second-half as well; Arnautovic hit the bar with a looping header for West Ham, but they were very much second best.
Juan Mata attempts to break the deadlock with a deft effort but sees his effort saved by a sprawling Hart
West Ham striker Javier Hernandez, on his return to his former club, tries to bypass Manchester United defender Eric Bailly
West Ham goalkeeper comes of his line to prevent Lukaku from sealing his hat-trick by punching the ball away from the area
The other huge positive for United, meanwhile, was the performance of Matic, a £40m suicide note from whichever member of Chelsea's transfer brains trust was running the show that week.
Matic controlled the game in the heart of midfield, protecting the back four – not that West Ham offered much in the way of threat – and releasing Pogba by his side. The Frenchman scored United's fourth of the game, following a neat pass from Martial, his low shot curling out of the reach of the forlorn Hart.
Despite Lukaku's impact, Matic's was probably the man of the match performance and will only have added to the funk settling on the shoulders of Chelsea manager Antonio Conte.
He seemed exactly the type of player they needed at Stamford Bridge on Saturday, and just what they have been missing at Old Trafford of late. And Conte, more than anyone, will appreciate that this Manchester United team would have looked plenty good enough, even without favours.
West Ham manager Slaven Bilic has a discussion with his Manchester United counterpart Jose Mourinho on the touchline
England manager Gareth Southgate watches from the Old Trafford stands with assistant coach Steve Holland
Former Manchester United manager Sir Alex Ferguson takes his seat in the directors' box before the match at Old Trafford