Microsoft's formally announced Halo 4 at the end of its press conference, confirming it for a holiday 2012 launch.
The game, which sees the return of Master Chief and AI companion Cortana, is being made by 343 Industries, and is the start of a brand new trilogy.
The trailer showed Chief been waken from an articifical sleep, as shown at the end of Halo 3, with the ship they were in exploding and heading towards an even bigger ship.
And that's your lot. Trailer's below. More soon.