Sorry, it was a mistake!
As we expected, HMV have said that the pre-order for MGS4 on the Xbox 360 was an error.It seems an over-zealous admin bod, rather than implementing a notification system for the possible future release of Metal Gear Solid 4 on the Xbox 360, hit the wrong button and launched a pre-order page instead.
HMV have apologised for causing a stir over the weekend.
However, this mistake has added fuel to the fire that the MGS series may move from being a PS platform exclusive and, given the success of GTA on other platforms, it would be likely...
In related news, PS3 owners have apparently backed down on their plans to storm HMV using cardboard boxes to cunningly conceal their arrival.
