Just in case you didn’t know, in the HMCC trailer after Master Chief detonates the bomb and pushes it towards the covenant cruiser a hand pops up blocking the bright explosion but that hand is actually Agent Locke as you can see Master Chief for a brief second floating there, I don’t have a link to the trailer and you may have already noticed it but I thought it was pretty cool and something I personally missed at first! 
I thought this was a given? The entire trailer is Agent Locke watching Chief’s past adventures.