Hope it's not too late to add some questions. I'm really grateful that you're sharing this opportunity
I'm not sure what kind of information he has or what kind of information he can even give... But here goes...
1) I'd like to know some basic stuff about his work. Like what his responsibilities are precisely. For example, does he or has he ever recruited sources and collected intelligence from people on the ground? Does he or has he ever worked in interrogation? Perhaps he's an analyst? Or maybe what he does is in fact more of an office job? So what does his job look like?
2) It would be great to find out more about the different intelligence organizations involved in the wars in Afghanistan and Iraq and how they cooperate.
On the US side of things there's the military intelligence, the CIA and the FBI (am I forgetting somebody else?). I've heard stories of these organizations not cooperating well together. Even stories of US military interrogators in Afghanistan exchanging information with British intelligence officers rather than with the CIA because with the British intelligence they had a give and take relationship whereas the CIA would refuse to give them most information and would often leave them without the information necessary to interrogate a suspect (like where and why the suspect was caught!).
So I'd be curious to know how all of that works. I'm not sure how much he'll be able to say about this, but anything he can would be great. Even if it's very mundane stuff I'd still be very curious about that.
3) A follow up on the previous question - how many intelligence organizations are actually involved in gathering intelligence about terrorist activity in Western nations, as well as the wars in Afghanistan and Iraq? I've heard practically nothing about the involvement of intelligence organizations from outside of the USA and UK. Yet that doesn't sound right - so many countries are involved in these wars that one would think they all have a vested interest in gathering intelligence. How does all that work?
4) Why is he stationed in Vegas? I know that might be a stupid question, but I'm genuinely curious. I don't get why a British military intelligence officer would be stationed in Vegas of all places.
5) What kind of places has his job taken him and where has he been stationed before? What were the circumstances?
6) What kind of access to terrorist suspects do different intelligence organizations have? Or if he's not able to answer quite so generally - has the British military intelligence ever had access to the prisoners in Guantanamo? If yes, then in what way and in what way were they limited? Have they ever had access to prisoners in CIA secret prisons?
I'm not sure how valid this line of questioning will be as it depends a lot on what he actually does and what kind of people he knows, but I'd love to know more about the interrogation process and how different organizations vary their approach.
7) What can he say about CIA secret prisons? I suppose the answer might be not much, but I'd still love it if you could try that line of questioning. I'm particularly interested in the CIA prisons which were rumoured to be in Poland, Lithuania and Romania. Though the topic of secret prisons is generally something I'd like to know as much as possible about.
8) How does he feel and what does he know about the torture of terrorism suspects in Guantanamo and other such places? US intelligence were allowed certain controversial practices, but how does the stance of the British military intelligence differ? Is he aware of any conflicts between British and American intelligence organizations over such practices? What about between different American organizations? (I've heard, for example, that the CIA has a harsher policy than the FBI) Has he spoken to American intelligence officers about such matters and how do they feel about it?
9) Has he ever been face to face with somebody incarcerated for terrorism in Guantanamo or a similar place? If yes, then what was that like? If no, does he know somebody who has - what were their feelings?