Manchester United will start 2013 with a seven-point lead at the top of the Premier League table after a hard-earned win over West Bromwich Albion.
Gareth McAuley deflected Ashley Young's cross past Ben Foster for the opening goal at a rain-lashed Old Trafford.
Foster tipped a Young effort onto the bar, before West Brom's Gabriel Tamas wasted a great close-range chance.
But United substitute Robin van Persie sealed victory with a curling finish in the 90th minute.
This was not as comfortable for United as the scoreline might suggest, with the leaders forced to weather a spirited second-half display from the Baggies.
Nevertheless the outcome was a welcome early birthday present for Sir Alex Ferguson, who is 71 on Monday.
The United manager starts the new year with a 13th Premier League title firmly within his sights after his side ended a trophyless 2012 with a victory sprinkled with positives.
Shinji Kagawa, back from a knee injury, was influential in his first appearance since October while captain Nemanja Vidic helped United to only their fourth Premier League clean sheet of the season.
Ferguson could even afford to start with Van Persie on the bench ahead of Tuesday's match at Wigan Athletic.
If there were any grumblings from the home dressing room it was that they forced their fans to endure a tense second half after struggling to add to their early lead until Van Persie's arrival.
West Brom deserve praise for the way they reacted after falling behind, with Steve Clarke's side showing why they arrived in Manchester in sixth place in the table.
Despite the soggy conditions United passed it around in their usual effortless style. And the hosts broke the deadlock in the ninth minute when McAuley diverted Young's low cross into his own net after Graham Dorrans gifted United possession with a careless clearance.
West Brom gave United a scare or two after half-time but Robin van Persie's delightful finish capped a victory which ensures Manchester United are well placed at the top of the table at the start of 2013
Young, one of five players recalled to the United side, then unleashed a powerful drive from 16 yards which Foster did well to tip onto his bar.
Michael Carrick was denied by Tamas's clearance off the line before half-time yet the West Brom player was guilty of a glaring miss during his team's best period after the interval.
The Romanian defender was presented with a glorious chance to equalise from close range but instead headed the ball away from the United goal.
Peter Odemwingie also went close in front of the Stretford End before Van Persie completed the scoring with a delightful 90th-minute finish.
Three days earlier Ferguson had berated the match officials during his side's narrow win over Newcastle but this time he celebrated from the touchline as Van Persie curled the ball over Foster from the edge of the area for his 14th league goal of the season.
Manchester United manager Sir Alex Ferguson:
"He (Robin van Persie) is a fantastic player. He came on and changed the game for us.
"Every time the ball came up to him he got hold of it and turned on them. They were having to go back to their box all the time and he has done well.
"West Brom were a very resilient, stubborn team. They worked really hard on their defending and closed all their ranks.
"You have to deal with that but the slowness of the pitch killed our speed a bit."
West Brom manager Steve Clarke:
"The fact they had to bring some of their big guns off the bench shows how well we were doing.
"In the first half we were too timid.
"We spoke at half-time about being too respectful and in the end, the scoreline doesn't reflect the way we played."
Live Text Commentary
Full Time The referee blows for the end of the match.90:00 +4:02
Jonny Evans concedes a free kick for a foul on Romelu Lukaku. James Morrison takes the indirect free kick.90:00 +2:44
Billy Jones takes a shot. Blocked by Nemanja Vidic.90:00 +2:22
James Morrison fouled by Danny Welbeck, the ref awards a free kick. Ben Foster takes the indirect free kick.90:00 +1:47
Corner taken by George Thorne from the left by-line played to the near post, Patrice Evra manages to make a clearance.89:58
Assist on the goal came from Antonio Valencia.89:58 Goal scored
Goal! - Robin van Persie - Man Utd 2 - 0 West Brom Robin van Persie fires in a goal from just outside the penalty box high into the middle of the goal. Man Utd 2-0 West Brom.89:39
Short corner taken by Ashley Young. Paul Scholes takes a shot. Shane Long gets a block in.89:22
Danny Welbeck takes a shot. Save by Ben Foster.88:31
Chris Smalling fouled by Shane Long, the ref awards a free kick. Free kick taken by Nemanja Vidic.86:44
Pass corner from left by-line crossed in by James Morrison, Patrice Evra manages to make a clearance.86:21
Peter Odemwingie takes a shot. Clearance by Nemanja Vidic.84:45
The ball is crossed by Liam Ridgewell, clearance by Nemanja Vidic.81:54 Substitution
Substitution Marc-Antoine Fortune joins the action as a substitute, replacing Graham Dorrans.81:54 Substitution
Substitution Paul Scholes on for Tom Cleverley.81:32
Robin van Persie takes a shot. Save by Ben Foster.79:19
Graham Dorrans takes a shot. Jonny Evans gets a block in.78:48
Corner taken by James Morrison from the left by-line to the near post, clearance by Robin van Persie.77:33
Ashley Young takes a shot. Save made by Ben Foster.76:52
Foul by Liam Ridgewell on Robin van Persie, free kick awarded. Chris Smalling takes the free kick.
Peter Odemwingie takes a shot. Nemanja Vidic gets a block in.75:14
Peter Odemwingie takes a shot. Blocked by Jonny Evans.73:56 Substitution
Substitution (West Brom) makes a substitution, with James Morrison coming on for Chris Brunt.71:31
Gareth McAuley fouled by Robin van Persie, the ref awards a free kick. Free kick taken by Gareth McAuley.71:09
Peter Odemwingie takes a shot. Chris Smalling gets a block in.69:37
Inswinging corner taken left-footed by Chris Brunt, Foul by Gareth McAuley on Chris Smalling, free kick awarded. David De Gea takes the free kick.67:30
Chris Brunt gives away a free kick for an unfair challenge on Ashley Young. Free kick taken by Chris Smalling.66:42
Chris Brunt takes the outswinging corner, Nemanja Vidic manages to make a clearance.66:06 Substitution
Substitution Romelu Lukaku is brought on as a substitute for Markus Rosenberg.66:06
The assistant referee flags for offside against Chris Smalling. Ben Foster takes the indirect free kick.65:47
Michael Carrick crosses the ball, Markus Rosenberg manages to make a clearance.64:57
Gabriel Tamas makes a clearance.64:57 Substitution
Substitution (Man Utd) makes a substitution, with Robin van Persie coming on for Shinji Kagawa.64:57
Corner taken by Robin van Persie from the right by-line,64:46
Antonio Valencia takes a shot. Save by Ben Foster.62:14 Booking
Booking Antonio Valencia is cautioned.62:02
Peter Odemwingie fouled by Antonio Valencia, the ref awards a free kick. Gabriel Tamas restarts play with the free kick.61:05
Corner taken by Ashley Young from the left by-line to the near post, clearance by Chris Brunt.59:38
Chris Brunt takes the inswinging corner, clearance by Jonny Evans.59:15
The ball is sent over by Peter Odemwingie, Graham Dorrans takes a shot. Patrice Evra gets a block in.56:03
Outswinging corner taken right-footed by Ashley Young from the right by-line, save by Ben Foster.55:45
Antonio Valencia takes a shot. Liam Ridgewell gets a block in.55:09
Inswinging corner taken right-footed by Ashley Young from the left by-line.54:43
Ashley Young crosses the ball, Antonio Valencia takes a shot. Liam Ridgewell gets a block in.53:56
Chris Brunt has an effort at goal from outside the box which goes wide left of the goal.53:44
Shane Long delivers the ball, Jonny Evans manages to make a clearance.53:28
Centre by Shane Long, Nemanja Vidic manages to make a clearance.53:12
Shane Long delivers the ball, clearance by Nemanja Vidic.52:38
Free kick awarded for an unfair challenge on Chris Smalling by Peter Odemwingie. David De Gea restarts play with the free kick.51:44
Gareth McAuley takes a shot. Blocked by Nemanja Vidic.50:28
Jonny Evans gives away a free kick for an unfair challenge on Shane Long. Chris Brunt delivers the ball from the free kick left-footed from right wing.49:40
Chris Brunt takes a shot. Save by David De Gea.48:17
Shinji Kagawa takes a shot. Blocked by George Thorne.47:57
The ball is crossed by Tom Cleverley, Gabriel Tamas manages to make a clearance.46:27
Free kick awarded for a foul by Markus Rosenberg on Ashley Young. Ashley Young takes the free kick.45:01
The referee gets the second half started.45:00 +1:43 Half time
Half Time The players leave the pitch at half time.45:00 +0:36
Foul by Tom Cleverley on Billy Jones, free kick awarded. Shot on goal comes in from Chris Brunt from the free kick, blocked by Antonio Valencia.44:39
Free kick awarded for a foul by Jonny Evans on Shane Long. Free kick crossed left-footed by Chris Brunt, Nemanja Vidic makes a clearance.39:37
Effort from the edge of the box by Peter Odemwingie goes wide of the left-hand upright.38:53
Tom Cleverley crosses the ball.38:20
The ball is swung over by Antonio Valencia, Gareth McAuley makes a clearance.36:04
Outswinging corner taken from the right by-line by Ashley Young, Nemanja Vidic has a headed effort at goal from close in which goes wide left of the goal.34:12
The ball is swung over by Peter Odemwingie.32:45
Inswinging corner taken right-footed by Ashley Young from the left by-line, Michael Carrick takes a shot. Gabriel Tamas manages to make a clearance.32:10
Centre by Antonio Valencia, Shot by Ashley Young. Ben Foster makes a save.30:47
Graham Dorrans fouled by Patrice Evra, the ref awards a free kick. Free kick crossed by Chris Brunt, Tom Cleverley makes a clearance.30:10
Ashley Young has a header from deep inside the six-yard box and clears the crossbar.29:50
Danny Welbeck takes a shot. Blocked by Graham Dorrans.24:19
Michael Carrick takes a shot. Blocked by George Thorne.20:01
Danny Welbeck is adjudged to have handled the ball. Ben Foster takes the free kick.18:25
Corner taken right-footed by Ashley Young.17:17
Danny Welbeck takes a shot. Ben Foster makes a save.15:28
Free kick awarded for an unfair challenge on Shane Long by Nemanja Vidic. Free kick taken by Liam Ridgewell.12:19
The ball is delivered by Antonio Valencia, clearance made by Billy Jones.8:43
Ashley Young provided the assist for the goal.8:43 Goal scored
Goal! - Gareth McAuley - Man Utd 1 - 0 West Brom Gareth McAuley concedes an unfortunate own goal. Man Utd 1-0 West Brom.8:41
Ashley Young produces a cross.6:19
Corner taken right-footed by Ashley Young from the right by-line, Nemanja Vidic has a header from close range and clears the crossbar.6:08
The ball is crossed by Antonio Valencia, Liam Ridgewell gets a block in.3:19
Graham Dorrans takes a shot and went wide of the left-hand upright.1:55
George Thorne concedes a free kick for a foul on Ashley Young. Free kick taken by Ashley Young.0:00
The ref blows the whistle to start the match.
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