Last time a flew in a Tutor (a couple of months ago), the procedure prior to looping was a steep bank one way to check below followed by a reversal to check the otherside, then a good lookout above to make sure it's all clear.
I'm sure any AEF guys out there will correct me if this isn't SOP.
If they we're manouvering when they collided it may have just been one of those occasions where they were in each other's blind spots and simply didn't see each other.