The win lifts Alex Ferguson’s men three points clear of second-placed Liverpool, who will travel to Wigan Athletic on Wednesday.

Bulgarian striker Dimitar Berbatov gave United the lead on 22 minutes with a cool finish past Scott Carson in the West Brom goal.

In the 40th minute WBA skipper Paul Robinson was shown straight red for a two-footed tackle on Park Ji Sung, and from there the game was one-way traffic for United.

The Red Devils scored again before the end of the first half, after Carlos Tevez took advantage of Carson’s blunder from Ryan Giggs’ corner.

The home side had one chance to get back in the game but Ryan Donk’s effort hit the post. Moments later, Nemanja Vidic raised to head another Giggs corner past Carson.

Cristiano Ronaldo scored twice on 65 and 73 minutes to wrap up his team’s big win.

In other games, Emile Heskey scored on his Aston Villa debut to help his team secure a 1-0 away win over Portsmouth.

Kenwyne Jones scored the only goal of the game, as Sunderland beat Fulham 1-0 at the Stadium of Light.

Tottenham cruised past Stoke City thanks to strikes from Aaron Lennon, Jermaine Defoe and Michael Dawson. James Beattie scored the visitor’s consolation on 57 minutes.