Surprise in store at the Electronic Entertainment Expo

Valve Software's first presentation at the Electronic Entertainment Expo has been pulled, to be replaced by what is being termed a "surprise."

Valve is the developer and publisher behind the juggernaut Half-Life and Left 4 Dead series, as well as owner of the PC and Mac game distribution network Steam, and the company's June 14 presentation was to be its E3 stage debut.

Initially slated as a reveal of the upcoming Portal 2, a follow-up to the 2007 hit Portal, Valve sent out a press release purporting to be from Aperture Science, the advanced technology company featured in the first game.

"Even though the cancellation of the event certainly counts as a surprise, we are pleased to further announce that the cancellation of the event is not THE surprise," it read.

Portal 2 has been mischievously teased in a number of ways after the company first inserted a cluster of radios into the original game in March, containing coded hints as to the nature of a sequel.

The press conference was originally scheduled for June 14, 7pm PST (2am June 15, GMT), and would have been broadcast by G4TV.

What Aperture Science's big surprise could be remains anyone's guess, ranging from a more inventive reveal of Portal 2, to news about Half-Life 2's long awaited Episode Three, to the possibility that Episode Three has been transformed into a full-blown version of Half-Life 3.

G4TV have been appointed the Expo's official broadcaster, and their coverage can be found at G4TV.com/e32010.