United - and Cristiano Ronaldo - produced a masterclass in the first 25 minutes. It was Ronaldo after just three minutes who opened the scoring for United.
Ronaldo seemed well covered by Lucas Neill but the Hammers skipper slipped as he tried to turn. No second invitation was required for Ronaldo to burst into the box and unleash a shot which flicked off George McCartney and flew into the net.
With less than three minutes on the clock, it was exactly what Sir Alex Ferguson would have wanted, although Patrice Evra was required to make a goal-line clearance to keep United in front after Edwin van der Sar failed to collect James Tomkins' looping header.
United were soon dominant, with West Ham struggling to contain their fluid attacking play.
Ronaldo doubled his goal tally - and United's - as he reacted coolly to a deep cross from Owen Hargreaves to turn the ball past West Ham keeper Robert Green.
Then it was former West Ham star Carlos Tevez's turn to steal the show with a magnificent 30-yard shot that was too hot for Green to handle. The Hammers' away support showed great class in applauding the magnificant strike.
But once Ashton had pulled one back, Nani inexplicably lost his composure and left referee Mike Riley with no alternative after head-butting Neill following a penalty-box fracas, although the Australian made the most of the clash.
United revised their formation at the break, using Ronaldo as a lone front-man and Tevez in a wider area.
West Ham should have been doing more than they were and any lingering hopes of a comeback were extinguished when Michael Carrick was allowed to amble 20 yards towards the visitors box without any challenge being made.
The Geordie then took aim and saw his second goal of the campaign fly in off Neill.
The result leaves United three points clear of second-placed Chelsea, who should they lose on Monday against Newcastle will hand the title to Ferguson's men.