Paul Pogba and Romelu Lukaku celebrate one of the latter's goals in the 4-0 hammering of West Ham.Romelu Lukaku began his career at Manchester United in fantastic fashion by scoring a brace as the Red Devils hammered West Ham 4-0 in their opening Premier League game of the new season at Old Trafford. The big Belgian opened his Premier League account for the Red Devils with a fine strike with United’s first attempt on target, before powering in a header in the second half to complete his brace. Anthony Martial came off the bench to score the third, before Paul Pogba completed the route.First HalfIt has often been said that Manchester United have struggled to play with as much fluency as they did under the legendary Sir Alex Ferguson. Under David Moyes, the looked tepid and frightened to go on the offensive. Under Louis van Gaal, well, the story wasn’t too much different either. It was also far from perfect last season, which was Mourinho’s first.But the first 45 minutes at Old Trafford today can arguably be said to be their best 45 minutes of football post Ferguson, and for good reason.The Red Devils began this game with so much riding on it: Romelu Lukaku and Nemanja Matic’s debuts, and Chicharito’s return to Old Trafford since being sold two years ago. And also, given the fact the Hammers haven’t beaten United at Old Trafford in a decade.And it began brightly for Mourinho’s men, who passed the ball around nicely, with Matic looking like he has finally found where he belonged.The Red Devils pressed and pressed, but never troubled Joe Hart in goal for West Ham, until the 33rd minute, as Matic made a great interception in midfield, passed on to Marcus Rashford, who plays a neat ball into the path of Lukaku, who then makes room for a shot and sends in a low drive which bounces in off the left post. He gets his first Premier League goal on his debut. That goal proved to be United’s first and only attempt on goal in the first half, as Lukaku’s opener was the difference as both sides went into the break.Second HalfIf you thought the Hammers would come into the second period all guns blazing and creating their own chances and dominating play, you were in for the same as the first half as it was United who continued to boss possession Slaven Bilic’s side struggling to contain them.One of the biggest problems the Red Devils had last season was their failure to convert the plethora of chances they created – their failure to see games off – and that anxiety looked to be setting in, as the game progressed with United still yet to trouble Hart in the half, despite having the bulk of possession.But all that would change in the 53rd minute, when Henrikh Mkhitaryan sends a perfect freekick in, and Lukaku manages to jump highest near the penalty spot and plants a cracking header low inside the right post. It's 2:0. He gets a brace on his Premier League debut. What a way to start his Manchester United career.West Ham were not without their moments, but they were barely noticeable. Diafra Sakho came off the bench and his first touch resulted in a corner for them, but nothing threatening came off of it as United continued to press and keep things tidy and keep possession of the ball. Marko Arnautovic then produced a header which hits the crossbar, but that was much as the Red Devils got as a scare.Rashford then goes close, as he decided to surprise the goalkeeper with a quick shot from the edge of the box, but his effort came back off the right post. That should have been the third of the game.Anthony Martial then came off the bench to make it three, before Paul Pogba completed the route to end the scoreline 4-0.