Mat Tonkang:
This is off-topic, but just to confirm - the AAIB's work at Lockerbie was purely technical, determining the break-up sequence from the point the bomb went off. It had no jurisdiction on the who, only the how.
Back on topic, the AAIB *is* a branch of the Civil Service, but it is a very different beast to the NTSB. What they do have in common is that they are both politically neutral, so if EMI had not been ruled out, or at least downgraded, they would have mentioned it as a possible contributing factor in the interim reports regardless of where it came from. Their remit is to figure out what happened - nothing more - and by all accounts they are extremely good at it and are world-respected as a result.