Jose Mourinho declared himself a happy man after watching Manchester United take West Ham apart in a 4-0 thumping at Old Trafford on Sunday.

Romelu Lukaku marked his Premier League debut for the club with a brace, before Anthony Martial and Paul Pogba added late gloss to the scoreline.

Since Alex Ferguson's retirement in 2013, United have been widely criticised for producing turgid, pedestrian displays devoid of attacking verve under David Moyes, Louis van Gaal and in Mourinho's maiden season in charge.

But they were full of vim and vigour against the Hammers, the pace and power of the likes of Lukaku, Marcus Rashford and substitute Martial proving too much for Slaven Bilic's side, leaving Mourinho satisfied with his side showing signs they are full of confidence.

"The game was difficult, it was open, at 2-0 they had a chance and I don't think the game was a 4-0," Mourinho told Sky Sports. "Then we scored a third and you breathe and relax. The reality of the game was it was always a difficult game for us.

"We didn't start especially well, we started nervous but then we had a quality performance, good personality and the team played with lots of confidence.

"Even at 2-0 the team was confident and playing football and I'm happy.

"We lost two points against West Ham here [last season] and had lots of similar matches where we dominated but did not score enough goals. Today we did and it's three important points.

"It's about confidence. In the last 20 minutes if they score it's 2-1 and the game is open, you feel the pressure and it would be entertaining but the reality is in the last part of the game, instead of being boring and controlling the game we scored a third goal."

And Mourinho was especially pleased to see Lukaku, after his £75million switch from Everton, follow in the footsteps of a host of other debutants on the Premier League's opening weekend in getting off the mark for their new employers.

"It's always important, new players in new clubs - everybody expects goals from them," he said.

"It's nice for [Alvaro] Morata to score, nice for Wayne Rooney to score and Lukaku and [Alexandre] Lacazette, it's always nice for that confidence."