I dropped amazon support a line and their response - 'the halo 4 available on Amazon UK is a PAL version and will not work on a US XBox.' J.Earl comment above is completely opposite.. not sure what to do.. :(
Yeah I got that same response when I tried to buy the PAL version of Halo 4. BAsically the store told me that they can't say that it will work on your machine because if it doesn't, they can be held liable because they said it would be fine (essentially accidentially lying to you). But trust me, I bought the PAL version and my US xbox plays it fine. Was able to play online and the campaign. I haven't tried Spartan Ops yet so I cant tell you if that is region locked or not, but basic multiplayer and campaign works fine.
I can now confirm that Spartan Ops does work as long as you still have a connection to Xbox Live US. Im in the Uk, but my live connection is still to the US, so I can play Spartan Ops. I don't think it will work if you have a UK connection because Spartan Ops in DLC, and almost all DLC is region locked. BUt for me, Halo 4 UK version works perfectly in my xbox. Im using an HDMI cable, not AV cables though, so that also may be a factor.
Thanks Earl.. you been a great help. Though the Spartan ops makes it a bit more confusing. I think i'm connecting to Xbox live UK. I guess I'll just pick up the PAL version of Halo 4 and see what all works.
i Have US Version and it works on a Pal Xbox (US Version is Region Free, same as UK version, Ger Version, Ita Version, FR version, ES version and so on (cant tell about the Jap version)) and all Codes and Preorder stuff too (redeemed on a Euro Country Account)